Comparative Biology and Ecology of the Formosan Subterranean Termite, Coptotermes Formosanus Shiraki (Isoptera: Rhinotermitidae) in Louisiana

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2000 Comparative Biology and Ecology of the Formosan Subterranean Termite, Coptotermes Formosanus Shiraki (Isoptera: Rhinotermitidae) in Louisiana. Huixin Fei Louisiana State University and Agricultural & Mechanical College

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Recommended Citation Fei, Huixin, "Comparative Biology and Ecology of the Formosan Subterranean Termite, Coptotermes Formosanus Shiraki (Isoptera: Rhinotermitidae) in Louisiana." (2000). LSU Historical Dissertations and Theses. 7194. https://digitalcommons.lsu.edu/gradschool_disstheses/7194

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. COMPARATIVE BIOLOGY AND ECOLOGY OF THE FORMOSAN SUBTERRANEAN TERMITE, COPTOTERMES FORMOSANUS SHIRAKI (ISOPTERA: RHINOTERMITIDAE) IN LOUISIANA

A Dissertation Submitted to the Graduate Faculty of the Louisiana State University and Agricultural and Mechanical College in partial fulfillment o f the requirements for the degree of Doctor of Philosophy in The Department of Entomology

by Huixin Fei B. S., Nanjing Agricultural University, 1986 M. S., Nanjing Agricultural University, 1989 May 2000

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. UMI Number 9979258

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UMI Microform9979258 Copyright 2000 by Bell & Howell Information and Learning Company. All rights reserved. This microform edition is protected against unauthorized copying under Title 17, United States Code.

Bell & Howell Information and Learning Company 300 North Zeeb Road P.O. Box 1346 Ann Arbor, Ml 48106-1346

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ACKNOWLEDGEMENTS

I would like to thank my major professor, Dr. Gregg Henderson, for his support,

encouragement, friendship, and guidance in every aspect throughout my graduate

studies and the course of this work, as well as in the writing of this dissertation. I am

gratefixl to my advisory committee, Drs. Abner M. Hammond, Seth J. Johnson, Richard

N. Story, and Lynn R. LaMotte for their assistance in formulating my study and

research schedule, their valuable inputs in my research, and their help in preparing this

dissertation.

I would like to thank Chris Dunaway, Jay Paxson, Beverly Wiltz, Jian Chen, and

Karen Nix for their assistance in collecting termites, maintenance of termite colonies in

the laboratory, and preparing this dissertation.

Thanks go to Dr. Frank S. Guillot, Department Head, and Dr. Linda Hooper-Bui,

who reviewed my paper in SOCIOBIOLOGY. Gratitude is also extended to the faculty

and staff of the Department of Entomology and a number of student workers who

offered assistance in various ways.

My deepest appreciation goes to my wife, Wenli Jing, and my daughter, Xianhan

(Mary) Fei for their love and encouragement throughout my work on this degree. I

thank them for understanding all long hours and late dinners.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. TABLE OF CONTENTS

ACKNOWLEDGEMENTS...... ii

LIST OF TABLES...... v

LIST OF FIGURES...... vii

ABSTRACT...... x

CHAPTER I. INTRODUCTION...... 1 « References ...... 10

II. COMPARATIVE STUDY OF INCIPIENT COLONY DEVELOPMENT IN THE FORMOSAN SUBTERRANEAN TERMITE, COPTOTERMES FORMOSANUS SHIRAKI (ISOPTERA: RHINOTERMITIDAE) IN LOUISIANA...... 17 Introduction ...... 18 Materials and Methods ...... 20 Results...... 25 Discussion ...... 27 References ...... 43

III. EFFECTS OF TEMPERATURE AND SOLDIER PROPORTION ON WOOD CONSUMPTION AND TERMITE SURVIVAL BY THE FORMOSAN SUBTERRANEAN TERMITE, COPTOTERMES FORMOSANUS SHIRAKJ (ISOPTERA: RHINOTERMITIDAE) 47 Introduction ...... 48 Materials and Methods ...... 49 Results...... 51 Discussion ...... 56 References ...... 63

IV. EFFECTS OF WOOD VOLUME AND SURFACE AREA ON WOOD CONSUMPTION RATE AND TERMITE SURVIVAL BY THE FORMOSAN SUBTERRANEAN TERMITE, COPTOTERMES FORMOSANUS SHIRAKI (ISOPTERA: RHINOTERMITIDAE) IN THE LABORATORY...... 67 Introduction ...... 68 Materials and Methods ...... 69 Results...... 73 Discussion ...... 80 References ...... 82

iii

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. V. EFFECT OF TERMITE DENSITY ON WOOD CONSUMPTION AND TERMITE SURVIVAL BY THE FORMOSAN SUBTERRANEAN TERMITE, COPTOTERMES FORMOSANUS SHIRAKI (ISOPTERA: RHINOTERMITIDAE)...... 86 Introduction ...... 87 Materials and Methods ...... 88 Results...... 90 Discussion ...... 91 References ...... 97

VI. EFFECTS OF MOISTURE AND TWO NITROGEN SOURCES ON NEST SITE CHOICE BY ALATES AND DEALATES OF COPTOTERMES FORMOSANUS SHIRAKI (ISOPTERA: RHINOTERMITIDAE) IN THE LABORATORY...... 100 Introduction ...... 101 Materials and Methods ...... 102 Results...... 104 Discussion ...... 105 References ...... 110

VII. SUMMARY...... 113

APPENDIX: LETTER OF PERMISSION...... 117

VITA ...... 118

i v

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. LIST OF TABLES

1.1: A list of stock colonies, collection sites, and collection time ...... 21

1.2: A list of incipient colonies started in 1996 (n=l 55) ...... 24

1.3: A list of incipient colonies started in 1997 (n=183) ...... 24

1.4: Test the equality of survival trends between males and females paired with either sibling or nonsibling mates using the Wilcoxon test ...... 31

1.5: Test the equality of survival trends paired in 1996 with either sibling or nonsibling pairs using the Wilcoxon test ...... 32

1.6: Test the equality of survival trends paired in 1997 with either sibling or nonsibling pairs using the Wilcoxon test ...... 33

1.7: Mean numbers of eggs in sibling- and nonsibling-founded colonies of C. formosanus during the 120-day observation ...... 34

1.8: The mean size of the two-year old C. formosanus colonies ...... 36

1.9: Mean numbers of larvae in sibling- and nonsibling-founded colonies of C. formosanus during the 300-day observation ...... 37

2.1: Effects of temperature and soldier proportion on survival of C. formosanus...... 52

2.2: Effects of temperature and soldier proportion on survival of C. formosanus at different observational times ...... 53

3.1: Differences in wood volume and surface area with different wood blocks for two C. formosanus colonies. Surface area I (S|) and surface area II (S2 ) nested within each level of wood volume (V) ...... 71

3.2: Results for testing the equivalent consumption rate (± SEM) by C. formosanus at different wood surface areas when equivalent wood volume was provided using Tukey's studentized range tests ...... 76

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 3.3: Effects of wood volume and wood surface area on wood consumption rate (x) with adjustment for termite survival at the test termination ...... 77

3.4: Mean percent survival of workers and mean soldier proportion (% ± SEM) in C. formosanus for both colonies. Means with the same letter are not significantly different using Tukey’s studentized range test ...... 80

4.1: Total wood consumption (mg wood ± SEM), mean wood consumption rate (mg wood / g termites per day ± SEM), mean percent survival (% ± SEM), and mean soldier proportion (% ± SEM) for nine treatments of termite densities in C. formosanus. Means separated by different letters indicate significant differences (p<0.05) using Tukey-Kramer HSD procedure ...... 92

5.1: Number of adults of C. formosanus in each Petri dish collected in the choice test ...... 106

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. LIST OF FIGURES

1.1: Incipient colonies containing moist paper towels (PT), floral blocks (FB), and wood blocks (WB) ...... 22

1.2: Comparison of survival rate (%) paired in 1996 with either sibling or nonsibling mates during the incipient stages of colony foundation ...... 28

1.3: Comparison of survival rate (%) paired in 1996 with either sibling or nonsibling mates during the incipient stages of colony foundation ...... 29

1.4: Comparison of survival rate (%) paired in 1997 with either sibling or nonsibling mates during the incipient stages of colony foundation ...... 30

1.5: Egg production rate in incipient colonies founded by sibling and nonsibling mates in 1997. Data are the mean and SD (standard deviation) ...... 35

1.6: Production of larvae in incipient colonies founded by sibling and nonsibling mates in 1997. Data are the average and SD (standard deviation) ...... 38

1.7: Percentage of presolders and soldiers in incipient colonies founded by sibling and nonsibling mates in 1997. Data are the mean and standard deviation ...... 39

2.1: Mean survival and SEM of C. formosanus cohorts under treatments of four temperatures at five observational times. Means separated by different letters indicate significant differences using Tukey-Kramer HSD procedure ...... 54

2.2: Mean survival and SEM of C. formosanus under five initial soldier proportions at five observational time. Means separated by different letters indicate significant differences using Tukey-Kramer HSD procedure ...... 55

2.3: Mean survival and SEM of C. formosanus at different temperatures and soldier proportions on 48 d (2.3-A) and 60 d (2.3-B). Means separated by different letters indicate significant differences using Tukey-Kramer HSD procedure ...... 57

vii

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 2.4: Mean proportions and SEM of soldiers in C. formosanus...... 58

2.5: Mean consumption rate and SEM in C. formosanus at different temperatures. Means separated by different letters indicate significant differences using Tukey-Kramer HSD procedure ...... 59

2.6: Mean consumption rate and SEM of C. formosanus at five soldier proportions. Means separated by different letters indicate significant differences using Tukey-Kramer HSD procedure ...... 60

3.1: Mean consumption rate and SEM by C. formosanus on blocks of Pinus sp., ranging in volume from 25.2 to 140cm^. Means with the same letter are not significantly different using Tukey*s studentized range test ...... 74

3.2: Mean consumption rate and SEM by C. formosanus on blocks of Pinus sp., ranging in volume from 25.2 to 140cm^. Means with the same letter are not significantly different using Tuke/s studentized range test ...... 75

3.3: Mean number of workers and SEM in C. formosanus on blocks of Pinus sp., ranging in wood volume from 25.2 to 140cm^ ...... 78

3.4: Mean number of workers and SEM in C. formosanus on blocks of Pinus sp., ranging in wood volume from 25.2 to 140cm^ ...... 79

4.1: Relationship of total wood consumption amount (y: mg wood) to termite density (x) in C. formosanus...... 93

4.2: Relationship of mean wood consumption rate (y: mg wood / g termites per day) to termite density (x) in C. formosanus...... 94

4.3: Relationship of percent survival of termites (y) to termite density of C. formosanus...... 95

4.4: Relationship of soldier proportion (y) to termite density in C. formosanus (x) at the termination of the experiment ...... 96

viii

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 5.1: Mean percentage (± SEM) comparison o f adults of C. formosanus collected in the test. Bars marked the same letter were not significantly different (p > 0.05) using Tukey’s mean comparisons test ...... 108

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ABSTRACT

A laboratory study was conducted to investigate the effects of sibship patterns and

different origins of colonies on mate mortality and growth of incipient colonies in the

subterranean termite, Coptotermes formosanus Shiraki. Primary reproductives from

New Orleans in nonsibling pairs had significantly higher mortality than sibling pairs.

The average egg production for sibling and nonsibling pairs showed no overall

significance in the first oviposition period, however, the average number of larvae was

consistently higher in nonsibling- than in sibling-founded colonies from New Orleans.

After two years, the average number of eggs or larvae present in nonsibling-founded

colonies was significantly higher than sibling-founded colonies from New Orleans.

Colonies headed by sibling pairs from Lake Charles showed the highest number of

larvae. Either sibling- or nonsibling-founded colonies from Lake Charles had a

significantly higher survival rate than colonies from New Orleans. The high mortality of

outbred pairs may be an effect of outbreeding depression or disease. The heterozygous

offspring by outbred pairs may provide advantages to environmental fluctuations and

harbor greater protozoan populations. Differences on survival and production of brood

between two areas may represent regional preadaptations.

In a second series of tests, it was determined that termite survival and wood

consumption were affected by a complex of factors. Termite cohort at 30 °C with initial

soldier proportions of 0 up to 10% produced a higher soldier proportion than those at 20,

25, or 33 °C. There was a significant interaction of temperature by soldier proportion on

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. termite survival. These two variables could not be isolated in our termite bioassay.

C. formosanus did not significantly increase wood consumption rate as termite density

increased. Termite survival and wood consumption rate declined significantly when

termite exceeded a density >300 individuals. Termite survival and wood consumption

rate significantly increased as wood volume increased. However, there was no

significant influence of wood surface area on consumption rate and survival, given a

constant wood volume. Moisture is a precondition for colonization by C. formosanus

queens and kings. Nitrogenous compounds of urea or L-glutamic acid in the moist

substrate did not increase nest site preference.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER I

INTRODUCTION

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. The order Isoptera is estimated to be 200 million years old (Borror et al. 1989).

Today, about 2761 termite species have been recorded in the world (Myles 1999). In the

United States, fewer termite species have been described than in Australia or China.

There are 45 described termite species in the United States belonging to four families:

Hodotermitidae (including Termopsidae), Kalotermitidae, Rhinotermitidae, and

Termitidae (Su & Scheffrahn 1990). Among these, the Formosan subterranean termite,

Coptotermes formosanus Shiraki, is considered the most destructive and aggressive

species in the southern United States (Bess 1970, Lai et al. 1983, Su & Tamashiro

1987). It is known to damage buildings, living trees, utility poles, and railroad ties. The

Formosan subterranean termite was first described in 1909 from South China (Abe

1937) and is believed to have originated in mainland China (Kistner 1985). Watson

et al. (1984) suggested that C. formosanus is a complex of species. However, in North

America, C. formosanus has shown high homogeneity in allozyme markers (Korman &

Pashley 1991), strongly suggesting the singularity of this species in the United States.

Cuticular hydrocarbon analyses have demonstrated quantitative variations in different

geographic populations of C. formosanus in the United States (Haverty et al. 1990).

In the continental United States, the Formosan subterranean termite was first

discovered in Houston, Texas in a shipyard in 1965 (Beal 1967). In 1966, well

established colonies of Formosan subterranean termites were discovered in New

Orleans and Lake Charles, Louisiana (King & Spink 1969, King 1971). It was

speculated that C. formosanus may have entered Louisiana near the end of the World

War II on military transport ships returning from the Orient (La Fage 1987). Presently,

in the United States, Formosan subterranean termites have been identified in Hawaii,

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Texas, Louisiana, California, Mississippi, Georgia, Alabama, Florida, Tennessee, South

Carolina, and North Carolina (Haagsma et al. 1995, Henderson personal

communication). In south Louisiana, C. formosanus is established in most parishes

(McMichael 1998).

Formosan subterranean termites belong to the most primitive genera within the

Rhinotermitidae (Bess 1970). They live in colonies, which have a social organization

similar to that of ants, some bees and some wasps. A colony consists of several castes,

which are physically different from each other and have their own particular duties to

perform that are directed towards the maintenance and survival of the colony (Stuart

1969). This phenomenon is called eusociality. Three traits are generally agreed upon as

characterizing eusociality (Wilson 1975): (1) conspecific individuals cooperate in brood

care, (2) there is a division of labor based on reproduction, and (3), at least two

generations serve in the labor force. However, the mechanisms and preadaptations for

eusociality in the Hymenoptera and Isoptera are very different. In the Hymenoptera, one

preadaptation for social behavior appears to have been haplodiploidy (males haploid,

females diploid) (Hamilton 1964a). Hamilton (1964b, 1972) proposed a hypothesis

which assigned central importance to the asymmetries in relatedness created by

haplodiploidy to explain multiple origins of reproductive division of labor in the

Hymenoptera. He argued that the multiple origins of reproductive division of labor in

the Hymenoptera could be explained by the haplodiploid mode of reproduction

characteristics of that group. As a result of haplodiploidy, female Hymenoptera are

more closely related to their sisters than to their own daughters. This process has been

termed kin selection and has been advanced as the explanation for the tendency of

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Hymenopteran societies to be characterized by altruistic behavior among sterile sisters

(Hamilton 1964b, 1972). Unlike Hymenoptera, however, both sexes of Isoptera are

diploid. Thus, explanations of eusocial evolution based on such asymmetries are not

applicable to termites (Hahn 1995; but see Syren & Luykx 1977). Bartz (1979)

proposed, by way of analogy with Hamilton's hypothesis, that the origin of sociality in

termites was based on asymmetry in relatedness as well. He proposed a possible routine

of termite evolution: prototermites lived under the bark or rotting wood because of the

predation pressure. These prototermites acquired the food source of their wooden refuge

with the assistance of symbiotic protozoa and became confined under the bark, leading

to increased opportunities for inbreeding. This inbreeding generates biases in

relatedness among individuals, allowing the evolutionary foundation for eusociality.

Once the local food source had been consumed, these prototermites would have had to

move to new food sources which favored outbreeding. Based on this scenario, Bartz

(1979) proposed that the life cycle of termites would lead to an alternation of inbreeding

and outbreeding which in turn would create asymmetries in relatedness. He suggested

that alates should be the offspring of replacement reproductives, and hence the progeny

should be highly inbred. These highly inbred alates should disperse and outbreed,

producing offspring that would be more closely related to their siblings than they would

be to their own offspring.

Cycles of inbreeding might be very important in some species of termites where

there is greater opportunity for sibling-replacement reproduction because colonies

persist for long periods (Noirot 1985, Myles & Nutting 1988). The mechanism,

however, poses potential difficulties for termites because inbred colonies suffer reduced

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. genetic variability that may make them susceptible to parasites and pathogens (Bateson

1983, Sherman et al. 1988). In addition, it is possible that replacement reproduction by

budding of worker groups also involves outbred matings (Lenz & Runko 1993).

According to Myles and Nutting (1988), colony longevity for some termite species is

too brief to be effective for cycles of inbreeding. Moreover, it is difficult to determine

the extent to which ancestral termites fit the premises of such a hypothesis (Thome

1997). Some alternative hypotheses have also been independently proposed to explain

the evolution of termite eusociality, such as the symbiont and nutrition transfer

hypotheses (Cleveland et al. 1934, Nalepa 1994), the chromosome-linkage hypothesis

(Luykx & Syren 1979, Lacy 1980), primer pheromones and soldier caste influence

(Henderson 1998), and the mixture of ecological constraints (Shellman-Reeve 1997,

Thome 1997). Recently, Rosengaus and Traniello (1993) examined the effect of the

sibship of primary reproductives on mate mortality, survivorship, and growth of

incipient colonies in the primitive dampwood termite, Zootermopsis angusticollis

Hagea They suggested that disease risk might decrease the success of outbreeding by

primary reproductives.

The Formosan subterranean termite is the one o f the most aggressive, difficult to

control, and economically important species of termites in the world (Su and Tamashiro

1987). To date, no information is available on the consequences of genetic relatedness

of primary reproductives that establish new colonies in any Rhinotermitidae.

Information about survivorship and fitness components of primary reproductives from

different sibships (sibling or nonsibling) will be helpful to our understanding of some

important biological and ecological characteristics of different breeding generations in

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. C. formosanus, and further, provide insight into how termite eusociality evolved. To

better understand the consequences of inbred and outbred relationships, a solid

foundation in proximate factors must be examined.

The swarm of winged reproductives (alates) of subterranean termites is an important

mode of forming new colonies from an established colony. Large swarms of Formosan

subterranean termites begin in April or May and end in July (Bess 1970, Higa &

Tamashiro 1983, Lin 1987, Henderson & Delaplane 1994, Henderson 1996). Formosan

subterranean termites are weak fliers; alates rarely fly more than a hundred meters

without assistance from wind (Higa & Tamashiro 1983, Henderson & Delaplane 1994).

After a short flight, alates drop to the ground, drop their wings and pair off. If they

successfully find a small crevice containing moist wood, the pair will form a chamber in

which the eggs are laid. When long-term moisture, food, and protection are available

away from the soil, the Formosan subterranean termites can form "aerial" infestations,

(Tamashiro et al. 1987). Previous studies indicate that temperature, humidity, rainfall,

light intensity, wind velocity, and atmospheric pressure affects the flight behavior of a

C. formosanus colony (Lai 1977, Lin 1987), although the direct relationship between

climatological factors and flight phenology is not obvious (Higa & Tamashiro 1983,

Henderson & Delaplane 1994). However, it has not been determined how specific

environmental factors may affect the nest site preference by founding pairs of the C.

formosanus. According to Huang and Zhang (1980), low reproduction and egg-hatching

rate by new founding pairs of C. formosanus corresponded with a reduction of moisture

on a diet in the laboratory. However, there is no direct evidence to indicate if moisture

affects the nest site preference by founding pairs of C. formosanus. In addition, nitrogen

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. availability has been recognized as an important nutritional constraint of wood feeding

termites (La Fage & Nutting 1978, Shellman-Reeve 1990). Nitrogenous compounds

have been reported to increase feeding by workers of C. formosanus (Henderson et al.

1994, Chen & Henderson 1996) and by the desert termite, Gnathamitermes tubiformans

(Buckley) (Spears & Ueckart 1976). Data are lacking to indicate whether nest-founding

pairs o f C. formosanus prefer sites with high nitrogen availability.

C. formosanus biology is similar to that of other subterranean termites (Bess 1970),

but differences are evident in colony size and development, nest building, foraging

activity, and damage. Aerial infestations that have no connection to the ground

frequently occur in urban areas (Su & Tamashiro 1987). According to a review by Su

and Tamashiro (1987), a mature Formosan subterranean termite colony contains

between 350,000 individuals and 4,000,000 individuals. By comparison, a mature

Reticulitermes flavipes (Kollar) colony is estimated to contain ca. 60,000 to 225,000

individuals (Haverty 1976). Unlike native subterranean termites, nest galleries in

Formosan subterranean termites are usually much cleaner, practically free of soil (Spink

1967). A laboratory study indicated that C. formosanus will make more penetrating

tunnels on wood blocks than Reticulitermes species (Delaplane & La Fage 1990).

Another difference is in their attack of living trees. This termite attacks living plants in

at least 41 families (Lai et al. 1983, La Fage 1987, Chambers et al. 1988). In Louisiana,

C. formosanus attacks 23 known living plant species (La Fage 1987). In Lake Charles,

Louisiana, the number of living trees infested by C. formosanus (6.5%) was

significantly higher than living trees infested by Reticulitermes species (1.1%)

(McMichael 1998). Finally, the foraging population of C. formosanus may consist of

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. several interacting colonies (Henderson 1996). In the laboratory, C. formosanus can

connect tunnels by the mixed groups of amicable non-nestmates (Chen & Henderson

1997). Large colony size and high reproductive potential of C. formosanus may partially

explain the rapid occurrence and severity of damage to infested building. Larger

colonies may also have greater advantages in disease resistance (Rosengaus et al. 1998).

Like most termites, C. formosanus eats cellulose, usually in the form of wood. C.

formosanus strongly preferred certain species of trees in laboratory choice tests (Smythe

& Carter 1970, Waller & La Fage 1987) and in the field in Lake Charles, Louisiana

(McMichael 1998). Food preference depends partly on the presence of allelochemicals

in wood, wood species, physical cues on wood, and microbes that modify wood (Wood

1978, Waller & La Fage 1987, Delaplane & La Fage 1989a, 1989b). C. formosanus

generally has a higher feeding rate on wood when compared with those of other

subterranean termites (Smythe & Carter 1970, Su & La Fage 1984a, Delaplane & La

Fage 1990). In the laboratory, feeding rates of C. formosanus on Pinus sp. varied from

45mg wood eaten / g termites / day to 114 mg /g termites / day (Delaplane 1991).

Formosan subterranean termites can adjust their search activity associated with

available food size in the laboratory (Hedlund & Henderson 1999). According to

Hedlund and Henderson (1999), excavation rate, tunnel volume, termite number, and

soldier number of C. formosanus were negatively correlated with the available food

source (white spruce).

Food consumption rates and termite survival have been used as indicators in many

laboratory bioassays and insecticide evaluations (Lenz et al. 1982, Su & La Fage

1984a). Attempts to study the whole colony under field conditions are usually not

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. practical because of large colony size and the difficulty in observing and manipulating

subterranean termites that live in cryptic sites. However, several factors are known to

affect the results of bioassays in the laboratory. These include ambient temperature,

food type, rearing matrix, group size, and intracolony or intercolony competition (Lenz

& Barrett 1984, Lenz 1995). In C. formosanus, the feeding rate varies by season (Waller

& La Fage 1987c), caste ratio (Su & La Fage 1987), and colony robustness (Su &

La Fage 1984b). Results of bioassays are complicated by the fact that there may have

interaction effects between factors on wood consumption and termite survival. Recent

interest in the use of toxic baits for control of subterranean termites has raised similar

questions for measuring bait toxicant efficacy in regard to bait consumption and termite

presence. Only after fully understanding not only the chemical but also environmental

factors which mediate the feeding behavior will it be possible to evaluate bait efficacy.

An insect may develop better at a given temperature on one diet than on another

(Slansky & Rodriguez 1987). Lenz et al. (1982) measured the influence of diet on the

survival and wood consumption of Porotermes adamsoni (Froggatt) at different

temperatures. Their results showed a significant temperature by timber type (sound or

decayed wood) interaction on wood consumption. Lenz (1995) measured the wood

consumption rates with R.flavipes with different sizes o f wood. They found that wood

consumption differed by about 200% for 1ml (0.5g) groups of termites kept on a block

of only 24cm^ as compared to those of 192cm^. In the field, Formosan subterranean

termites encounter a choice of wood that may be influenced by temperature, caste

composition, wood size, population density, and the interactions among these and other

factors. In order to provide more information on the biology and ecology of Formosan

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. subterranean termites so that bioassay techniques and evaluation on termite baits can be

more efficiently conducted, a series of experiments were conducted in this study to

evaluate possible effects on food consumption and termite survival under one or more

ecological conditions.

References

Abe, Y. 1937. On the distribution o f the oriental termite, Coptotermes formosanus Shiraki in Japan. Sci. Rep. Tohoku Univ. 11:463-472.

Bateson, P. P. G. 1983. Optimal outbreeding. In: Mate Choice, pp. 257-277. Bateson, P. P. G (ed.). Cambridge University Press, Cambridge, England.

Bartz, S. H. 1979. Evolution o f eusociality in termites. Proc. Natl. Acad. Sci. 76:5764-5768.

Beal, R. H. 1967. Formosan invader. Pest Control. 35:13-17.

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Delaplane, K. S. and J. P. La Fage. 1990. Wood excavations of three species of subterranean termites. Entomol. Exp. Appl. 54:81-87.

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Henderson, G. and K. S. Delaplane. 1994. Formosan subterranean termite swarming behavior and alate ratio (Isoptera: Rhinotermitidae). Ins. Soc. 41:19-28.

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King, Jr., E. G. and W. T. Spink. 1969. Foraging galleries of the Formosan subterranean Termite, Coptotermes formosanus Shiraki in Louisiana. Ann. Entomol. Soc. Am. 62:536-542.

Kistner, D. H. 1985. A new genus and species of termitophilous Aleocharinae from mainland China associated with Coptotermes formosanus and its zoogeographical significance (Coleoptera: Staphylinidae). Sociobiology. 10:93-104.

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La Fage, J. P. 1987. Practical considerations of the Formosan subterranean termite in Louisiana: a 30 year -old problem,. In :The Biology and Control of the Formosan Subterranean Termite, pp. 37-42. Tamashiro, M. & N. -Y. Su (eds.). College Trop. Ag. Human Resources, University of Hawaii, Honolulu, Hawaii.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. La Fage, J. P. and W. L. Nutting. 1978. Nutrient dynamics of termites. In: Production Ecology of Ants and Termites, pp. 165-232. Brian, M. V. (ed.). Cambridge University Press, Cambridge, England.

Lai, P. Y., 1977. Biology and ecology o f the Formosan subterranean termite, Coptotermes formosanus and its susceptibility to the entomogenous fungi, Beauveria bassiana and Metarrhizium anisopliae. Ph.D. Dissertation, Department of Entomology, University of Hawaii, Honolulu, Hawaii. 123 pp.

Lai, P. Y., M. Tamashiro, J. R. Yates, N. -Y. Su, J. K. Fujii and R. H. Ebesu. 1983. Living plants in Hawaii attacked by Coptotermes formosanus. Proc. Hawaii Entomol. Soc. 24:283-286.

Lenz, M. 1995. Food resources, colony growth and caste development in wood-feeding termites. In: Nourishment and Evolution of Insects, pp. 159-210. Hunt, J. H. & C. A. Nalepa (eds.). Westview Press Inc., Boulder, Colorado.

Lenz, M. and R. A. Barrett. 1984. Implications for comparability of laboratory experiments revealed in studies on the effects of population density on vigor in Coptotermes lacteus (Froggatt) and Nasutitermes exitiosus (Hill) (Isoptera: Rhinotermitidae & Fermitidae). Bull. Ent. Res. 74:477-485.

Lenz, M. and S. Runko. 1993. Long-term impact o f orphaning on field colonies of Coptotermes lacteus (Froggatt) (Isoptera: Rhinotermitidae). Ins. Soc. 40:439-56.

Lenz, M., R. A. Barrett and E. R. Williams. 1982. Influence of diet on the survival and wood consumption of Porotermes adamsoni (Froggatt) (Isoptera: Termopsidae) at different temperatures. Bull. Ent. Res. 72:423-435.

Lin, S. -Q. 1987. Present status of Coptotermes formosanus and its control in China. In: The Biology and Control of the Formosan Subterranean Termite, pp. 31-36. Tamashiro, M. & N. -Y. Su (eds.). College Trop. Ag. Human Resources, University of Hawaii, Honolulu.

Luykx, P. and R. M. Syren. 1979. The cytogenetics of Incisitermes scwarzi and other Florida termites. Sociobiology. 4:191-209.

McMichael, J. A. 1998. Survey of subterranean termites (Isoptera: Rhinotermitidae) in trees in Sam Houston Jones State Park, West Lake, Louisiana. Master’s Thesis, Department of Entomology, Louisiana State University Agricultural Center, Baton Rouge, Louisiana. 85 pp.

Myles, T. G. and W. L. Nutting. 1988. Termite eusocial evolution: a re-examination of Bartz’s hypothesis and assumptions. Q. Rev. Biol. 63:1-23.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Myles, T. G. 1999. Phylogeny and taxonomy of the Isoptera. Proceedings of XIII International Congress o f IUSSI. December 29, 1998-January 4, 1999. Adelaide, Australia, p. 334.

Nalepa, C. A. 1994. Nourishment and the origin o f termite eusociality. In: Nourishment and Evolution in Insect Societies, pp. 57-104. Hunt, J. H. & C. A. Nalepa (eds.). Westview Press, Colorado, Oxford.

Noirot, C. 1985. Pathways o f caste development in the lower termites. In: Caste Differentiation in Social Insects, pp. 41-57. Watson, J. A. L., B. M. Okot-Kotber & C. Noirot (eds.). Oxford Pergamon, Oxford.

Rosengaus, R. B. and J. F. A. Traniello. 1993. Diseases risk as a cost of outbreeding in the termite Zootermopsis angusticollis. Proc. Natl. Acad. Sci. 90:6641-6645.

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Shellman-Reeve, J. S. 1990. Dynamics of biparental care in the dampwood termite, Zootermopsis nevadensis (Hagen): response to nitrogen availability. Behav. Ecol. Socio. 26:389-397.

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Slansky, F. and J. G. Rodriguez. 1987. Nutritional ecology of insects, mites, and spiders: an overview. In: Nutritional Ecology of Insects, Mites, and Spiders, pp. 1-50. Slansky, F. & J. G. Rodriguez (eds.). Wiley and Sons, New York.

Smythe, R. V. and F. L. Carter. 1970. Feeding responses to sound wood by Coptotermes formosanus, Reticulitermes flavipes, and R. virginicus (Isoptera: Rhinotermitidae). Ann. Entomol. Soc. Am. 63:841-847.

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Spink, W. T. 1967. The Formosan subterranean termite in Louisiana. Louisiana State University Cir. 89. 12 pp.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Stuart, A. M. 1969. Social behavior and communication. In: Biology of Termites. Vol. I. pp. 193-347. Krishna, K. & F. M. Weesner (eds.). Academic Press. New York.

Su, N. -Y. and J. P. La Fage. 1984a. Comparison o f laboratory method for estimating wood consumption rates by the Formosan subterranean termite, Coptotermes formosanus Shiraki (Isoptera: Rhinotermitidae). Ann. Entomol. Soc. Am. 77:125-129.

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Tamashiro, M., J. R. Yates and R. H. Ebesu. 1987. The Formosan subterranean termite (Isoptera: Rhinotermitidae) in Hawaii: problems and control. In: The Biology and Control of the Formosan Subterranean Termite, pp. 15-26. Tamashiro, M. & N. -Y. Su (eds.). College Trop. Ag. Human Resources, University of Hawaii, Honolulu.

Thome, B. L. 1997. Evolution o f eusociality in termites. Annu. Rev. Ecol. Syst. 28:27-54.

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Waller, D. A. and J. P. La Fage. 1987b. Food quality and foraging response by the subterranean Coptotermes formosanus Shiraki (Isoptera: Rhinotermitdae). Bull. Ent. Res. 77:417-424.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Waller, D. A. and J. P. La Fage. 1987c. Seasonal patterns in foraging groups of Coptotermes formosanus (Rhinotermitdae). Sociobiology. 13:173-181.

Watson, J. A. L., D. Zi-Rong and R. A. Banett. 1984. Comparative studies on the resistance of materials to species of Coptotermes (Isoptera: Rhinotermitidae). I. The susceptibilities of various plastics to Coptotermes acinaciformis (Froggatt) from Australia and Coptotermes formosanus Shiraki from China. Bull. Ent. Res. 74:495-503.

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER II

COMPARATIVE STUDY OF INCIPIENT COLONY DEVELOPMENT IN THE FORMOSAN SUBTERRANEAN TERMITE, COPTOTERMES FORMOSANUS SHIRAKI (ISOPTERA: RHINOTERMITIDAE) IN LOUISIANA

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Introduction

Insect eusociality has evolved in two phylogenetically unrelated orders: the

Hymenoptera (some wasps, bees, and all ants) and the Isoptera (all termites) (Wilson

1971). One genetic hypothesis proposes that a relatedness asymmetry (higher

relatedness between alloparent and brood than between parent and brood) accounts for

the origins of eusociality (Hamilton 1964a, 1964b, 1972, Bartz 1979). In Hymenoptera,

a relatedness asymmetry exists as a result of the haplodiploid genetic system. Termites

are diploid, and the theory applied to the Hymenoptera species does not explain the

ancestral condition in the eusociality of termites. Several hypotheses have been

proposed to explain the evolution of eusociality in termites (see Cleveland et al. 1934,

Syren & Luykx 1977, Bartz 1979, Luykx & Syren 1979, Lacy 1980, Myles & Nutting

1988, Nalepa 1994, Shellman-Reeve 1997, Thome 1997, Henderson 1998). Among

these theoretical models, genetic mechanisms proposed to explain eusociality in termites

have been extensively debated. In some species of termites, translocation complexes of

sex-linked chromosomes may favor eusociality through higher relatedness since at loci

on these chromosomes, same-sexed siblings are more highly related to each other than

to opposite-sex siblings or to their own offspring (Syren & Luykx 1977, Luykx & Syren

1979, Lacy 1980). However, no permanent interchange complexes of sex-linked

chromosome have been discovered in Coptotermes formosanus Shiraki (Wang & Grace

1999), suggesting the higher relatedness among sibs that might arise from large

complexes of sex-linked chromosomes is not a sufficient cause in the evolution of

eusociality in this species. Bartz (1979) proposed a pattern of cyclic inbreeding and

outbreeding that would generate and maintain asymmetries in relatedness among colony

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. members. It is impossible to evaluate the reality of this type of hypothesis on the

evolution of termite eusociality because the hypothesis examines the case before

establishment o f eusocial system (Thome 1997). However, as suggested by Shellman-

Reeve (1999), the evaluation of the consequences of genetic relatedness on nest-

founding reproductives is essential to understand the genetic basis of colony

cooperation.

One solution to assess the consequences of genetic relatedness is the use of DNA

markers that can be used to obtain the relatedness estimate among colony members

(Pamilo 1984, Pamilo et al. 1997, Reeve et al. 1992, Vargo & Henderson 1999).

Microsatellite markers may be powerful tools for examining population genetic

structure in subterranean termites (Vargo & Henderson 1999). An alternative method is

to determine the survivorship and fitness of nest-founding reproductives (Rosengaus &

Traniello 1993). A laboratory study on nest-founding pairs of Zootermopsis

angusticollis Hagen indicated that nonsibling pairs suffer higher mate mortality during

the incipient stages of colony foundation, suggesting to the authors that disease risk may

decrease the success of outbred pairs (Rosengaus & Traniello 1993). The objective of

the present study was to determine the consequences of genetic relatedness among

paired dealates of primary reproductives by examining the survivorship and fitness of

inbred and outbred pairs of C. formosanus in Louisiana. It is hypothesized that

differences in sibship patterns (sibling or nonsibling) and the different origins of

parental colonies can significantly affect mate mortality and incipient colony dynamics

of C. formosanus. Ecological stresses (low temperature and no food provided) on the

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. C. formosanus population fitness and mate survival also were evaluated in the sibling-

and nonsibling-founded colonies.

Materials and Methods

Termite Collection. Stock colonies of C. formosanus were collected in 1996

through 1997 at two localities: New Orleans and Lake Charles, Louisiana (Table 1.1).

Three stock colonies (colonies 1, 2, and 4) were transferred from collecting sites into

plastic containers (52cm diam. x 72cm high) and maintained in separate laboratory

rooms kept at 24—28 °C. Alates from these laboratory colonies were collected as they

flew using light traps (BioQuip Products, Gardena, CA) placed on top of the plastic

containers. Alates from the other stock colonies were collected directly from nest

materials with the aid of forceps just prior to or during flight. Stocks in New Orleans

were collected from infested trees. In Lake Charles, stocks were collected from infested

oak trees (Quercus sp.). Sexes were determined by examining the terminal abdominal

sterna of alates with the aid of a stereoscopic microscope. Chilling (4 °C for ca. 2 min.)

was used to immobilize alates for sexing. Subsequently, they were placed in separate

arenas to form pairs. After pairing, the wings of alates usually were quickly shed, in

some cases, the wings were removed with the aid of forceps. Only healthy alates were

used in the experiment.

Laboratory Colony Establishment and Culturing. Each pair was formed from

either the same stock colony (sibling pair) or different stock colonies (nonsibling pair).

Each pair was put into a plastic Petri dish (45mm diam. x 90mm high) with moist paper

towel (Choremaster®, GA) and approximately 1 lcm^ acetone-washed floral block

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Table 1.1. A list o f stock colonies, collection sites, and collection time.

Stock colony Location Collection time

Colony 1 New Orleans May 13, 1996 Colony 2 New Orleans May 21, 1996 Colony 3 New Orleans June 10, 1996 Colony 4 New Orleans April 28, 1997 Colony 5 New Orleans May 29, 1997 Colony 6 Lake Charles May 28, 1996 Colony 7 Lake Charles May 7, 1997

(FloraCraft®, MI) which served as moisture source (Figure 1.1). Small wood blocks

approximately 0.5cm^ each of Pinus sp. served as a food source and were continuously

replaced as needed. All incipient colonies received wood blocks from the same source

of wood. Moisture was kept constant throughout the duration of the test. Incipient

colonies were maintained in a laboratory room with temperatures of 24-28 °C for

incipient colonies paired in 1996 and maintained in incubators at 27 ± 0.1 °C for

incipient colonies formed in 1997.

A total of 155 incipient colonies were formed in 1996 (Table 1.2). In 1997, a total of

183 incipient colonies were set up (Table 1.3). Because all colonies were not established

on the same date, results were standardized by analyzing data in terms of time elapsed

since pairing of primary reproductives.

Colony Census and Measurements. Data on mortality of kings and queens

(primary reproductives) and developmental rates were recorded by examining each

incipient colony once each 4-day interval for the first 60 days after establishment of

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure Figure 1.1. (WB). blocks (FB), wood blocks and (PT), colonies towels paper moist containing floral Incipient H PL,

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. colonies and approximately once every 10 days for an additional 60 days thereafter.

After 120 days, colonies were examined once every two months. Colony developmental

rates were obtained by recording the number of days elapsed to the appearance of the

first egg and the number of eggs and larvae present in each incipient colony at various

time intervals.

Evaluation of ecological stress on sibling- and nonsibling-founded incipient

colonies of C. formosanus. To compare the effect of low temperature (21 °C) and

hunger on the sibling- and nonsibling-founded incipient colonies of C. formosanus, 120

pairs were set up. Alates from stock colony 4 and stock colony 5 were collected for this

study. In the first test o f this study, sibling pairs (n=30, primary reproductives from

colony 4) and nonsibling pairs (n=30, primary reproductives from colony 4 and 5) were

formed and incubated at 21 °C with the same food source as described above. In the

second test, sibling pairs (n=30, primary reproductives from colony 4) and nonsibling

pairs (n=30, primary reproductives from colony 4 and 5) were provided with the

acetone-washed floral block only as described above and incubated at 27 °C. No other

food source was provided during the test. Observations were conducted by

recording mortality of primary reproductives and the numbers of eggs and larvae up to a

94-d observational period.

Data analysis. To compare the survival rate between different incipient colonies

with time course, the test for differences in proportions for dichotomous response was

conducted (Stokes et al. 1995). The nonparametric life table method was employed to

estimate survival rates of primary reproductives in different incipient colonies and

compare survival curves of primary reproductives in incipient colonies (SAS Institute

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Table 1.2. A list o f incipient colonies started in 1996 (n=l55).

Incipient colony Stock colony Location Pattern of king and queen of stock colony of sibship Al king: colony 1 New Orleans sibling (n=22) queen: colony 1 New Orleans A2 king: colony 2 New Orleans sibling (n=31) queen: colony 2 New Orleans A3 king: colony 6 Lake Charles sibling (n=30) queen: colony 6 Lake Charles B1 king: colony 1 New Orleans nonsibling (n=23) queen: colony 6 Lake Charles B2 king: colony 6 Lake Charles nonsibling (n=24) queen: colony 1 New Orleans B3 king: colony 2 New Orleans nonsibling (n=25) Queen: colony 3 New Orleans

Table 1.3. A list of incipient colonies started in 1997 (n=183).

Incipient colony Stock colony Location Pattern of king and queen of stock colony of sibship Cl king: colony 4 New Orleans sibling (n=50) queen: colony 4 New Orleans C2 king: colony 4 New Orleans nonsibling (n=80) queen: colony 5 New Orleans D1 king: colony 7 Lake Charles sibling (n=53) queen: colony 7 Lake Charles

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 1989, Allison 1995). The Wilcoxon-Mann-Whitney test and the Kruskal-Wallis test

were used to compare two or more parameters (e.g., the numbers of eggs and larvae) of

different incipient colonies (SAS Institute 1989, Stokes et al. 1995).

Results

Survival Rates. High mortality in primary reproductives was observed soon after

establishment of pairs, reaching averages o f 43% for males and 40% for females at 100

days after pairing. There were no significant differences in survival trends between

males and females for each type of incipient colonies (p>0.05, Table 1.4, Figures 1.2,

1.3, 1.4). Primary reproductives in nonsibling pairs had significantly lower survival

rates than sibling pairs based on an analysis of the time course of survival rates (p<0.05,

Figures 1.2, 1.3, 1.4) and the test of differences in survival trends (Tables 1.5, 1.6).

Furthermore, there were significant differences in the survival rate of primary

reproductives among incipient colonies originated from New Orleans and Lake Charles.

Nonsibling pairs from New Orleans showed significantly lower survival rates than

nonsibling pairs from Lake Charles (p<0.05, Figures 1.2, 1.3, 1.4, Tables 1.5, 1.6).

Sibling pairs from New Orleans had a significantly lower survival rate than sibling pairs

from Lake Charles (p<0.05, Figures 1.2, 1.3, 1.4, Tables 1.5, 1.6).

Production of Eggs. One hundred percent of the tested incipient colonies

produced at least one egg at 20 days after pairing. The time (± SD) to initiate egg laying

during the first oviposition stage was 9.37 (± 2.37; range, 4 - 20) days for 1996 and 6.83

(± 2.07; range, 4 - 12) days for 1997. There were no significant differences between

sibling and nonsibling-founded colonies for the time to initiate egg laying (p>0.05). The

egg production for sibling- and nonsibling-founded colonies from New Orleans showed

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. no significant differences in the first oviposition period (Table 1.7, Figure 1.5).

However, nonsibling pairs laid significantly more eggs than sibling pairs after two years

of colony foundation (x^-7.9953, p<0.0047, Table 1.8). Furthermore, an analysis of

time course indicated that incipient colonies headed by sibling and nonsibling pairs

from Lake Charles showed a significantly higher number of eggs than incipient colonies

from New Orleans (Table 1.7).

Production of larvae and soldiers. Nonsibling-founded colonies produced

significantly higher numbers of larvae than sibling-founded colonies (Table 1.9, Figure

1.6). Colonies originally headed by sibling pairs from Lake Charles produced

significantly higher numbers of larvae than sibling-founded colonies from New Orleans

(Table 1.9). An examination of the two-year old C. formosanus incipient colonies

indicated that the number of larvae was significantly higher in nonsibling-founded

colonies than the sibling-founded colonies (x^=4.4941, p<0.034, Table 1.8). Sibling-

founded colonies from Lake Charles showed significant higher number of larvae than

sibling-founded colonies from New Orleans (x^=7.6115, p<0.0058, Table 1.8).

The percentage of presoldiers and soldiers in either sibling-founded incipient

colonies or nonsibling-founded incipient colonies varied with the development of

incipient colonies (Figure 1.7). However, the soldier proportion was not significantly

affected by sibship pattern and stock colony origin. There were no significant

differences among colonies in the percentage of presoldiers and soldiers (x^-1.8797,

p=0.3907). After two years, the percent of presoldiers and soldiers did not show

significant differences between incipient colonies Cl and C2 (x^=0.8533, p=0.3556),

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. between incipient colonies Cl and D1 (x^=1.470, p=0.2253), and between incipient

colonies C2 and D1 (x^=0.5211, p=0.4704) (Table 1.8).

Evaluation of ecological stress on sibling- and nonsibling-founded incipient

colonies of C. formosanus. After 94 days of observations, no eggs or larvae were

observed in the incipient colonies headed by sibling and nonsibling pairs at 21 °C and

with no food provided. Apparently, the floral block provided some nourishment for the

king and queen to survival over three months. At 21 °C, no larvae were produced in

either sibling or nonsibling pairs during the observation, however, a significantly higher

number of eggs was observed in nonsibling pairs than sibling pairs (x^=4.7344,

p<0.0392). Furthermore, primary reproductives in nonsibling pairs had significantly

lower survival rate than sibling pairs either at 21 °C or with no food provided (p<0.05).

Under no food provided conditions, no significant difference was observed for the

production of larvae between sibling and nonsibling pairs (x^=0.8189, p=0.3894),

although the number of eggs in sibling pairs was significantly higher than nonsibling

pairs (x^=5.2740, p<0.0058).

Discussion

This study on incipient colony development in C. formosanus supports the

hypothesis that the origin of primary reproductives (kings and queens) can influence

mate survivorship and colony dynamics. The result that nonsibling pairs suffered

significantly higher mortality than sibling pairs is consistent with previous research on

Z. angusticollis (Rosengaus & Traniello 1993). However, our results indicate that the

decreased success of outbred mates in the early stage of colony development is offset by

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 100 Male

80 ■ —

70 -

60 2

— A l: Sibling, New Orleans — A2: Sibling, New Orleans B3: Nonsibling, New Orleans

4 8 12 16 20 24 28 32 36 40 44 48 52 56 60 70 80 90 100 110 120 180 Days after pairing

120

Female 100

2 60 > 3£ — A l: Sibling, New Orleans A2: Sibling, New Orleans 20 - B3: Nonsibling, New Orleans

4 8 12 16 20 24 28 32 36 40 44 48 52 56 60 70 80 90 100 110 120 180 Days after pairing

Figure 1.2. Comparison of survival rate (%) paired in 1996 with either sibling or nonsibling mates during the incipient stages of colony foundation.

Survival rate (%) Survival rate (%) 100 40 20 30 50 60 70 100 80 120 10 20 40 60 80 - 4

Female ■A3:Lake Charles Sibling, Lake Charles (Male) Charles Lake by New Orleans (Female) Nonsibling, B2: 12 (Female) Charles Lake by New (Male) Orleans Nonsibling, B1: Male

Lake Charles (Male) Charles Lake (Female) Charles Lake by 1:(Male) New Orleans Nonsibling, B Lake Charles Sibling, A3: B2: Nonsibling, New Orleans (Female) by New(Female) Orleans Nonsibling, B2: 16

32 1

36 Days after Dayspairing after Days pairing after

40 29

70 ■

100

110

120

180 120 Male

100

8 0 '

— 60

— C 1: Sibling, New Orleans C2: Nonsibling, New Orleans

20 Dl: Sibling, Lake Charles

4 8 12 16 20 24 28 32 36 40 44 48 52 56 60 70 80 90 100 120 130 215 300 430 570 728 Days after pairing

120 Female

1 0 0 - - i

80 -

—C3 60 - — C l: Sibling, New Orleans C2: Nonsibling, New Orleans D l: Sibling, Lake Charles 20 -

4 8 12 16 20 24 28 32 36 40 44 48 52 56 60 70 80 90 100 120 130 215 300 430 570 728 Days after pairing

Figure 1.4. Comparison of survival rate (%) paired in 1997 with either sibling or nonsibling mates during the incipient stages of colony foundation.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Table 1.4. Test the equality of survival trends between males and females paired with either sibling or nonsibling mates using the Wilcoxon test.

Incipient colony* Chi-square Pr > Chi-square

Al 0.0325 0.8569

A2 0.0189 0.8907

A3 0.0346 0.8524

Bl 0.3782 0.5385

B2 0.0348 0.852

B3 0.0009 0.9765

Cl 0.0172 0.9241

C2 0.0447 0.7836

Dl 0.2647 0.6362

* A l, A2, A3, C l, Dl: sibling; B l, B2, B3, C2: nonsibling (see Tables 1.2, 1.3).

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 0.0027 / 0.0024 0.0027 Pr > Chi-square (Male / Female) (Male > Chi-square Pr 0.557/0.7482 8.8988/ 10.1851 4.1806/5.7327 0.0316/0.0217 0.3449 / 0.3449 0.2357 0.0647/0.0114 0.7992/0.9152 * Al,* sibling; Bl, A3: A2, Table (see nonsibling B3: 1.2). B2, Bl +B2 B3 vs. A2 vs. A3 vs. A2 Bl vs. B2 Incipient colony* Incipient / Female) (Male Chi-square Al A3vs. 4.2575/5.3114 0.0312/0.0284 A1+A2 vs. vs. B3A1+A2 /5.3872 5.4271 / 0.0236 0.0232 Al A2 vs. Table 1.5. Test the equality of survival trends paired in 1996 with either sibling or nonsibling pairs using the Wilcoxon test. the pairs Wilcoxon using or nonsibling sibling with either paired in trends ofsurvival equality 1996 the Test Table 1.5.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 0.0292/0.0316 Pr > Chi-square (Male / (Male Female) Chi-square > Pr Chi-square (Male / Female) (Male Chi-square * Cl,* Dl: Table (see C2: nonsibling 1.3). sibling; C2 vs. vs. DlC2 32.485/31.059 / 0.0001 0.0001 Incipient colony* Incipient Table 1.6. Test the equality of survival trends paired in 1997 with either sibling or nonsibling pairs using the Wilcoxon test. the Wilcoxon pairs using or nonsibling eithersibling with paired in trends survival of equality 1997 Test the Table 1.6. Cl vs. Dl 4.7552/3.6713 Cl C2vs. 18.984/ 15.947 0.0001/0.0001 u>

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 5.7813.12a 1.0412.17a 2.1812.99a 8.3315.94b 2 .0 1 1.89a 4.83 1 3.40a during the 120-day observation. the during 120-day 13.4314.56b 9.8914.39b 1.812.78a 7.3416.01a 4.8614.87a 9.8916.74b 4.3 1 3.92a 3.013.61a C. formosanus C. 9.818.02a 9.3816.35b 11.8118.29b 18.0915.55b 16.1614.69b 10.5418.83a 12.4519.94a 10.62 ± 8.91a10.62 2 .0913.62a 13.36 ± 6.97a 13.36 2.4814.35a 7.2113.48a 6.8613.57a 6.5412.81a 8.7718.96a 1 3.5 6.37a 11.12 ± 7.45a 11.12 ± 5.66b 17.02 14.60 ± 5.42a 14.60 13.43 ± 3.98b 13.43 12.2 ± 4.91a 12.2 11.05 ± 5.88a 11.05 Egg number corresponding to days after pairing** pairing** after days to corresponding number Egg 10.56 ± 3.78a 10.56 11.07 ± 2.33a 11.07 12.03 4.13a ± 12.03 16-d 16-d 36-d 52-d 70-d 100-d 120-d 7.5 17.5 3.03a ± 3.75a 12.29 11.7716.29a 4.3 1 7.39a 1 4.5 5.20a 4.3217.39a 9.75 9.75 ± 3.46a 7.23 ± 4.23a 7.23 1.91a 2.43a4.20a ± 9.16 ±9.61a 11.8 2.29a 4.03a 4.72 ± 2.89a 10.14:14.42a 2.87 ± 2.87 4.04 ± 4.04 2.02a 2.37 ± 2.37 8-d * Al,* Cl, A3, A2, Dl: Bl,sibling; Tables (see C2: nonsibling 1.2, 1.3). B3, B2, a=0.05 at different the Wilcoxon- using by significantly are level different letters with ± SD. Means labeled mean are Data ** Mann-Whitney test for comparisons of two incipient colonies corresponding to days after pairing. after days to corresponding colonies two incipient ofcomparisons test for Mann-Whitney Dl ± 5.65 2.44a C2 ± 7.56 2.38a B2 Cl B3 ± 3.03 A3 Bl 1 5.15 1.46b ± 2.95b 11.05 ± 4.74b 16.7 17.714.92b 10.2713.84b A2 Incipient Al ± 3.09 Colony* Table 1.7. Mean numbers of eggs in sibling- and nonsibling-founded colonies of nonsibling-founded and sibling- ofin eggs numbers Mean Table 1.7.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Days afterpairing Days □Cl: Orleans New Sibling, □C2: Orleans New Nonsibling, ■Dl: Charles Lake Sibling, 888 4 8 12 16 20 24 28 32 36 40 44 48 52 56 60 70 80 90 100 120 130 215 300 430 570 728 Figure 1.5. Egg production rate in incipient colonies founded by sibling and nonsibling mates in nonsiblingand in mates sibling by colonies 1997. founded rate incipient production in Egg Figure 1.5. deviation). (standard and SD are the mean Data 10 30 25 20 ) CA BO 3 4 BO m O M 15 v E z C CA

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. (1SD) 12.3514.74 NS NS 8.614.21 % Presoldiers and soldiers soldiers Presoldiers and % (1SD) 1.3311.21 ±0.83 1.91 12.2719.43 3.811.48 Number of presoldiers and soldiers and soldiers presoldiers of Number colonies. (±SD) C. formosanus C. 10.8416.78 30.781 10.50 S SNS NS 22.21 ±11.2322.21 Number of Larvae of Larvae Number (±SD) 11.3315.71 S S** (n=22) (n=38) NS*** (n=26) 4.89 ±3.014.89 Number of eggs ofeggs Number ** S: significant difference between points at P<0.05. *** NS: no significant difference between points. Differences between between Differences points. between difference significant NS: no at *** P<0.05. between points difference significant S: ** * Cl,* Dl: Table C2: nonsibling (see 1.3). sibling; test. the by Wilcoxon-Mann-Whitney performed were means C2 vs. DlC2 vs. Cl C2 vs. Cl Dl vs. Colony DlColony ± 4.89 3.01 Colony C2 Colony Incipient Colony Cl Colony Colony* Table 1.8. The mean size of the two-year old old of the two-year size mean The Table 1.8.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. - - - - 300-d 19.6710.15b 20.4819.21b 10.7517.41c 180-d 2.331 1.66b - 8.3315.94c 0.2110.47a 0 .6 1 0.69a during the 300-day observation. during 300-day the 1.2111.14a 1.841 1.24b 7.7715.27a 10.416.17a 2 .5 1 1.66b 0 .8 1 0.78a C. formosanus C. 11.521 10.24cl0.33 18.40c 4.6614.41a 0.2210.44a 0.2710.63a 19.8618.06b 21.4318.36c 23.5818.22b 12.7110.73c 0 .3 1 0.47a 11.819.61c 12.4519.94c 9.3816.35c 11.8118.29c 4.9214.82a 4.72 1 4.22a Number of larvae corresponding to days after pairing** pairing** after days to corresponding oflarvae Number 10.1117.88b 11.9317.21b 15.5318.42b 16.8817.89b 19.9817.56b 6.28 ± 4.57a 6.28 70-d 70-d 80-d 90-d 100-d 120-d 11.47 ± 4.80b ± 4.80b ± 11.47 6.97b 12.04 ± 5.88b 13.8 7.36 ± 6.94a 7.36 5.78 ± 3.31b5.78 ± 6.92c 8.13 10.018.29c 2.42 ± 2.42 1.75b ± 2.1 1.48b 2.781 1.99b 2 .2 1 1.68b 2.4412.16b 2.87 12.87 2.43c4.20c ± 9.16 60-d 0.72 0.72 ± 0.90a ± 0.86 1.06a 0.2910.56a ** Data are mean followed by ± SD. Means labeled with different letters are significantly different at a=0.05 at different the using by significantly are different letters with level labeled ± Means SD. by mean followed are Data ** pairing. after days to colonies corresponding two ofincipient comparisons test for Wilcoxon-Mann-Whitney performed. were observations No *** * Al,* Cl, A3, A2, Dl: Bl,sibling; Tables (see C2: nonsibling 1.2,1.3).B3, B2, Dl B3 0.89 ± 0.78a ± 1.23b 1.8 1 .7 1 1.06b 2.381 1.96b 1.831 1.06b B2 Bl ClC2 4.82a ± 7.17 A3 Al Incipient A2 0.92 ± 1.24a ± 1.13a 1.18 0.5510.62a 0.4510.42a 0.5510.51a Colony* Table 1.9. Mean numbers of larvae in sibling- and nonsibling-founded colonies of colonies nonsibling-founded and sibling- in of numbers larvae Mean Table 1.9.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Days after pairing Days i l □Cl: Orleans New Sibling, □ Orleans New Nonsibling, C2: ■Dl: Charles Lake Sibling, Data are the mean and SD (standard deviation). and SD mean the are Data Figure 1.6. Production of larvae in incipient colonies founded by sibling and nonsibling mates in and nonsibling in mates sibling by colonies 1997. offounded larvae incipient in Production Figure 1.6. 4 4 8 12 16 20 24 28 32 36 40 44 48 52 56 60 70 80 90 100 120 130 215 300 430 570 728 15 10 35 45 40 30 25 eo a !» Z M u> oo

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 2802 Days after pairing after Days GC1: Orleans New Sibling, □ Orleans New Nonsibling, C2: ■Dl: Charles Lake Sibling, 4 4 8 12 16 20 24 28 32 36 40 44 48 52 56 60 70 80 90 100 120 130 215 300 430 570 728 Figure 1.7. Percentage of presolders and soldiers in incipient colonies founded by sibling and nonsibling andnonsibling sibling by colonies andfounded incipient soldiers presolders of in Percentage Figure 1.7. mates in 1997. Date are the mean and deviation. standard mean are the Date in mates 1997. 10 25 20 e u S 15 12 u CO fi a o' 2 '•5 ’o u> VO

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. an increased fecundity and survivorship of offspring among established colonies. In

addition, collection sites (New Orleans and Lake Charles) are strongly associated with

differences in mate mortality and incipient colony development.

The high mortality that occurred in nonsibling-founded colonies indicates that

outbreeding in C. formosanus has a negative effect on mates in the incipient stage of

colony foundation. Based on the results for Z angusticollis (Rosengaus & Traniello

1993) and the present study in C. formosanus, inbreeding might be relatively common

within a termite colony because no negative effects were observed on mate mortality. In

the model of Bartz (1979) and Hamilton (1972), the underbark or rotting wood habitat

of ancestral termites is considered to be confining and thus enforces inbreeding. It may

be common for termite colonies to produce sibling-replacement reproduction among

some multiple-site nesters or central-site nesters because colonies may live for longer

periods and because offspring may bud off from a parent’s nest (Shellman-Reeve 1997).

Although there exists the possible costs of inbreeding, where deleterious genes in

offspring are more likely to be fully expressed (Bateson 1983), the costs might be

lessened at the colony level given a sufficiently large pool of neotenics (Shellman-

Reeve 1997). Inbreeding is very common in Reticulitermes Jlavipes (Kollar) (Reilly

1987). The Reticulitermes colony contains numerous inbreeding neotenic reproductives

(non-alate derived reproductives, Thome 1996). Their numbers depend upon habitat,

colony size, and species (Weesner 1956, Thome et al. 1999). However, according to

Luykx et al. (1986), the primary reproductives appear to be typically outbred because of

differences in sexual development and sex dispersal. In C. formosanus, although lower

survival was observed among outbred pairs of primary reproductives, the reproductive

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. potential or direct fitness was significantly higher in outbred pairs. This suggests that

outbreeding may be of considerable importance, although there are costs in the early

stage of colony foundation. Furthermore, evidence indicates that the sex ratio of light-

trapped C. formosanus alates varies over time, thus enhancing the chance of outbreeding

in primary reproductives (Henderson & Delaplane 1994).

The high mortality of outbred pairs may be only an effect of outbreeding depression

because of the mismatch of habits acquired by mates in different environments (Bateson

1983) or disease because of the differences in acquired immune response to pathogens

(Rosengaus & Traniello 1993). Nonsibling pairs may acquire immunity to different

pathogens present previously in the different parental colonies, thus causing mortality

due to the possible transmission of pathogens from immune reproductives to non-

immune reproductives (Rosengaus & Traniello 1993). According to Wang and Grace

(1999), no permanent interchange complexes of chromosome were found in C.

formosanus, which may suggest a decline of opportunity for inbreeding within a colony.

The heterozygous offspring by outbred pairs may impact greater genetic variation and

provide greater adaptation to environmental fluctuations. The heterozygous offspring

may harbor greater protozoan populations and species composition due to outbreeding

of primary reproductives, a hypothesis that needs to be tested.

The lifetime of C. formosanus kings and queens appears to be relatively long

(Huang 1987). A colony maintained in the laboratory takes eight years to mature and at

that time the alates swarm (Huang & Chen 1984). Bess (1970) initiated and maintained

C. formosanus colonies for four years. King (1971) did a two and half year study on

incipient colonies of C. formosanus. Higa (1981) maintained a colony of C. formosanus

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. for five years in the laboratory. Consequently, no neotenics in C. formosanus colonies

were reported based on all these laboratory observations. However, many neotenics can

be observed from field C. formosanus colonies (Fei, unpublished observational data).

One hundred neotenics in two different field colonies in Honolulu have been reported

(Bess 1970), although very little information is available on their formation. It is

difficult to directly observe reproduction in the field for colonies of C. formosanus.

C. formosanus may have developed a mechanism such as the occurrence o f unequal sex

ratio with time of swarming to enhance outbreeding of primary reproductives. After

initiation by outbred primary pairs, colonies grow fast. The initial egg production and

colony growth appear to be crucial because kings and queens can not feed themselves.

Heterozygous offspring by outbred pairs may provide greater advantages in certain

environments. Once colonies expand, supplementary reproductives contribute to

budding of colonies and through inbreeding help to maintain genetic asymmetries

favorable to social evolution.

Like many introduced insect species, C. formosanus has rapidly spread its

distribution in the southern United States. In Louisiana, C. formosanus was considered

to be independently introduced into New Orleans and Lake Charles and it was suggested

that the Lake Charles population may represent an unidentified species of Coptotermes

(La Fage 1987). However, the singularity of this species is apparent (Korman & Pashley

1991). In the present study, incipient colonies were established successfully with

primary reproductives (kings and queens) which originated from two different locations,

i.e., New Orleans and Lake Charles. Significant differences in mate mortality and

colony dynamics among incipient colonies originated from New Orleans and Lake

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Charles is consistent with the hypothesis that the collection site of primary

reproductives is an important factor affecting incipient colonies. Similarly, depending

on the colony origin of primary reproductives, significant differences of colony size also

were observed among two-year old incipient colonies of R. flavipes in the laboratory

(Thome et al. 1997). These differences may reflect regional preadaptations of primary

reproductives that are associated with nutritional differences and adjustments to

microhabitats. Nutrients of the fat body of alates appear especially important for

successful production of initial offspring (Lenz 1987). In addition to nutrition,

differences of the relative abundance of the protozoa in the hindgut and adaptation to

pathogens may also have shaped the association of primary reproductives and local

environments. A recent interesting finding suggests that introductions of C. formosanus

to the United States came from at least two locations; one from China, and another from

an unknown source (Wang & Grace 1998). According to Wang and Grace (1998),

populations of C. formosanus from Lake Charles, Hawaii, Hong Kong (China), and

Guangzhou (China) differed from populations of C. formosanus from New Orleans and

Florida, suggesting different subspecies. The significant variability in C. formosanus

mate mortality and colony dynamics in these two areas, in fact, also may reflect a

subspecies characteristic.

References

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Bartz, S. H. 1979. Evolution o f eusociality in termites. Proc. Natl. Acad. Sci. 76:5764-68.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Bess, H. A. 1970. Termites of Hawaii and the oceanic Islands. In: Biology of Termites. Vol. II. pp. 449-476. Krishna, K. & F. M. Weesner (eds.). Academic Press, New York.

Bateson, P. P. G. 1983. Optimal outbreeding. In: Mate Choice, pp. 257-77. Bateson, P. P. G (ed.). Cambridge University Press, Cambridge.

Cleveland, L. R., S. R. Hall, E. P. Sanders and J. Collier. 1934. The wood-feeding roach Cryptocercus, its protozoa, and the symbiosis between protoza and roach. Mem. Am. Acad. Arts Sci. 17:185-342.

Hamilton, W. D. 1964a. The genetical evolution of social behavior. I. J. Theoret. Biol. 7:1-16.

Hamilton, W. D. 1964b. The genetical evolution of social behavior. II. J. Theoret. Biol. 7:17-52.

Hamilton, W. D. 1972. Altruism and related phenomena, especially in social insects. Annu. Rev. Ecol. Syst. 3:193-232.

Henderson, G. and K. S. Delaplane. 1994. Formosan subterranean termite swarming behavior and alate ratio (Isoptera: Rhinotermitidae). Ins. Soc. 41:19-28.

Higa, S. Y. 1981. Flight, colony foundation, and development of the gonads of the primary reproductives of the Formosan subterranean termite, Coptotermes formosanus Shiraki. Ph.D. Dissertation, Department of Entomology, University of Hawaii, Honolulu, Hawaii. 177 pp.

Huang, L. 1987. The growth of colony size in relation to increasing reproductive capacity of Coptotermes formosanus Shiraki. Acta Entomol. Sinica 30:393-396 (in Chinese with English abstract).

Huang, L. and L. Chen. 1984. Biology and colony development of Coptotermes formosanus Shiraki. Acta Entomol. Sinica 27:64-69 (in Chinese with English abstract).

King, Jr., E. G. 1971. Biology o f the Formosan subterranean termite, Coptotermes formosanus Shiraki, with primary emphasis on young colony development. Ph.D. dissertation. Department of Entomology, Louisiana State University Agricultural Center, Baton Rouge. 193 pp.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Korman, A. K. and D. P. Pashley. 1991. Genetic comparisons among U. S. populations of Formosan subterranean termites. Sociobiology. 19:41-48.

Lacy, R. C. 1980. The evolution of eusociality in termites: a haplodiploid analogy? Am. Nat. 116:449-51.

Lenz, M. 1987. Brood production by imaginal and neotenic pairs of Cryptotermes brevis (Walker): the importance of helpers (Isoptera: Kalotermitidae). Sociobiology. 13: 59-66.

Luykx, P. and R. M. Syren. 1979. The cytogenetics of Incisitermes schwarzi and other Florida termites. Sociobiology. 4:191-209.

Luykx, P., J. Michel and J. Luykx. 1986. The spatial distribution o f the sexes in colonies of the termite Incisitermes schwarzi Banks (Isoptera: Kalotermitidae). Ins. Soc. 33:406-21.

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Pamilo, P., P. Gertsch, P. Thoren and P. Seppa. 1997. Molecular population genetics of social insects. Annu. Rev. Ecol. Syst. 28:1-25.

Reeve, H. K., D. F. Westneat and D. Queller. 1992. Estimating average within-group relatedness from DNA fingerprints. Molec. Ecol. 1:223-232.

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Rosengaus, R. B. and J. F. A. Traniello. 1993. Diseases risk as a cost of outbreeding in the termite Zootermopsis angusticollis. Proc. Natl. Acad. Sci. 90:6641-6645.

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Stokes, M. E., C. S. Davis and G. G. Koch. 1995. Categorical data analysis using the SAS system. SAS Institute Inc., Cary, NC.

Syren, R. M. and P. Luykx. 1977. Permanent segmental interchange complex in the termite Incisitermes schwarzi. Nature. 266:167-68.

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Thome, B. L. 1997. Evolution o f eusociality in termites. Annu. Rev. Ecol. Syst. 28:27-54.

Thome, B. L., N. L. Breisch and J. F. A. Traniello. 1997. Incipient colony development in the subterranean termite Reticulitermes flavipes (Kollar) (Isoptera: Rhinotermitidae). Sociobiology. 30:145-159.

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Vargo, E. and G. Henderson. 1999. Polymorphic microsatellite loci in the subterranean termites Reticulitermes flavipes and Coptotermes formosanus. Proceedings of the National Entomological Society Meeting. December 12-15, 1999, Atlanta, Georgia, p. 97.

Wang, J. 1998. Genetic markers for populations and colonies of Coptotermes Wasmann (Isoptera: Rhinotermitidae). Ph.D. Dissertation, Department of Entomology, University of Haiwaii, Honolulu, Hawaii, 120 pp.

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Weesner, F. M. 1956. The biology of colony foundation in Reticulitermes hesperus Banks. Univ. Calif. Publ. Zool. 61:253-314.

Wilson, E. O. 1971. The insect societies. Belknap Press / Harvard University Press, Cambridge, Massachusetts.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER III

EFFECTS OF TEMPERATURE AND SOLDIER PROPORTION ON WOOD CONSUMPTION AND TERMITE SURVIVAL BY THE FORMOSAN SUBTERRANEAN TERMITE, COPTOTERMES FORMOSANUS SHIRAKI (ISOPTERA: RHINOTERMITIDAE)

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Introduction

The biotic and abiotic factors affecting termite survival and food consumption are

fundamental to the evaluation of termite vigor in the laboratory (Lenz & Williams 1980,

Lenz et al. 1982). These factors can also alter the effect of insect growth regulators on

colony dynamics (Haverty & Howard 1979, Su & La Fage 1986). If there are more

soldiers in a colony than the workers can support, food consumption will decrease and

the colony will die (Su & La Fage 1987, Oi 1994). Oi (1994) reported that cohorts of

Reticulitermes virginicus (Banks) workers could not sustain soldiers in excess of 20%

for longer than four weeks. In the Formosan subterranean termite, Coptotermes

formosanus Shiraki, wood consumption decreased significantly as soldier proportion

increased from 30 to 40% of the total population (Su & La Fage 1987). Juvenile

hormone analogs and mimics can cause an increase in soldier and pre-soldier

production with a subsequent decrease in workers, eventually causing total mortality of

the colony by disrupting the caste balance (Hrdy & Krecek 1972, Wanyonyi 1974, Chu

et al. 1974, Yin & Gillot 1975, Haverty et al. 1989, Su & Scheffrahn 1989).

Pyriproxyfen and fenoxycarb, two juvenile hormone mimics, have been reported to

suppress eastern and Formosan subterranean termite colonies in the laboratory and in

field trials (Jones 1984, Su & Scheffrahn 1989, Haverty et al. 1989). The termite colony

may exceed its maximum supportable soldier proportion because of the production of

especially high soldier number by the induction of juvenile hormone mimics (Haverty

& Howard 1981, Su & Scheffrahn 1990, Oi 1994).

The major reason increasing soldier numbers can cause colony mortality is because

workers must feed the soldiers. Morphological adaptations that provide supreme

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. defense capabilities set up the obstacle for soldiers from feeding (Henderson 1998),

therefore causing soldiers to be expensive to maintain. The average soldier proportion

for C. formosanus in a field or laboratory colony is 5 - 10% (Haverty 1977) which may

be the optimal soldier proportion, although in a foraging population, a 20 - 60% soldier

proportion was reported (Nakajima et al. 1964). Termite soldier proportions vary

seasonally and with the environmental conditions (Howard & Haverty 1981, Waller &

La Fage 1987, Waller & La Fage 1988, Delaplane et al. 1991). The mechanism that

regulates these environmental variations in soldier proportions is largely unknown.

Depending on the soldier proportion, termite cohorts may behave very differently at one

temperature than at another. The effect of possible interactions between temperature and

soldier proportion on food consumption and termite survival of C. formosanus has not

been previously considered. The objective of this study was to determine how ambient

temperature and different soldier proportions affect wood consumption and termite

survival. This study tests the hypothesis that effects of soldier proportions on termite

survival and wood consumption rates do not differ significantly at different

temperatures. The result of this study provides ecological information on how combined

factors of temperature and soldier proportions affect termite survival and wood

consumption in C. formosanus.

Materials and Methods

Termites. A C. formosanus colony was collected from an infested tree in New

Orleans, Louisiana and stored in a 250 liter container for about six months at 24-28 °C

before testing. Moistened corrugated cardboard rolls were used to collect termites

from the container (La Fage et al. 1983). Termites were gently knocked from the

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. cardboard rolls into clean plastic trays (20cm diam., 20cm height, Tristate Plastics,

Inc., Dixon, Kentucky) and separated from soil, wood and carton material using

moistened paper towels (Gay et al. 1955). For experimentation, termite mean worker

and soldier weights (± 0.01 mg) were determined by weighing ten groups of 50

individuals.

Food sources and assay arena. Termites were fed wood blocks which were cut by

a table saw from a single board of southern pine (Pinus sp.) that was free of knots. All

wood blocks measured 30 x 30 x 30mm. An experimental unit consisted of a glass

screw-top jar (4.5cm diam. x 5.0cm high, Alltrista Corporation, Muncie, Indiana)

containing 25ml of sand moistened with 9ml of deionized distilled water. Sand was

acetone washed and oven dried 6 h at 85 °C. Pine wood blocks were oven dried 56 h at

85 °C, weighed (± 0.01 mg), and submerged in distilled water 5 h before use. Wood

consumption rate was calculated as mg eaten wood / g worker / day (Haverty & Nutting

1974, Su & La Fage 1984).

Experimental design. A completely randomized design with a four x five

factorial structure was conducted. Four bioclimatic chambers were set up at 20, 25, 30,

and 33 °C ± 0.1 °C. Each experimental unit contained 100 termites (externally

undifferentiated larvae of at least the third instar) with 0, 10, 20, 30, or 40% soldiers.

There were a total of 20 experimental treatments (4 temperatures x 5 soldier

proportions). Each treatment was replicated 5 times for a total of 500 experimental

units. One hundred experimental units were randomly selected on day 12, 24, 36, 48,

and 60. These experimental units were then disassembled for counts of surviving

worker, soldier, and any pre-soldier and determination of their combined weights (±

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 0.01 mg). Wood blocks were also separated from the sand substrate, washed and oven

dried for 56 h at 85 °C for determination of wood consumption weights (± 0.01 mg).

Data analysis. To stabilize the variance, data on the survival rate of workers and

soldiers were arcsine square root transformed. Wood consumption rates were

transformed by log (x). Data were back-transformed for presentation purposes. Effects

of temperature and initial soldier proportion on the survival of each colony unit was

tested with multivariate ANOVA (MANOVA, Rencher 1995), followed by a

univariate F-test on each variable (SAS Institute 1989). The effect of these variables

on wood consumption by workers was similarly analyzed. All effects were evaluated

for significance using Type III sums of squares (SAS Institute 1989). Tukey-Kramer

HSD procedure was used for post-ANOVA comparisons at a=0.05 if the ANOVA

was significant. A simple linear regression analysis was conducted for each initial

soldier proportion at the four different temperatures. Soldier proportions were

considered the dependent variable at the termination of the test. Observational time

was the independent variable.

Results

Temperature and initial soldier proportion on survival and soldier

production. Termite survival was significantly affected by time (observational

period), temperature, soldier proportion, and all combinations of sources of variation

measured (Table 2.1). The low temperature of 20 °C did not significantly influence the

termite survival until 48 d of the test, where high mortality began to appear (Figure

2.1). Termite cohorts at 30 °C maintained highest survival rate after 36 d of the test

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Table 2.1. Effects of temperature and soldier proportion on survival o f C. formosanus.

Sources d f Mean F P of variation square Time (or observation)* 4 8.10 122.86 0.0001 Temperature 3 2.17 32.91 0.0001 Time x temperature 12 1.23 18.68 0.0001 Soldier proportion 4 5.58 84.59 0.0001 Time x soldier proportion 16 0.23 3.42 0.0001 Temperature x soldier proportion 12 0.12 1.80 0.0421 Time x temperature x soldier proportion 48 0.14 2.19 0.0001

T im e denotes five different observational periods (12, 24, 36,48, and 60 days).

(Figure 2.1). Termite survival was not influenced by initial soldier proportions at 12 d

of the test (Figure 2.2). On average, termites had a significantly higher survival rate

when initial soldier proportions were less than 20% at 12 d (Figure 2.2). When soldier

proportions were less than 10%, survival rate was highest for all observational times

(Figure 2.2).

Significant interactions of temperature by soldier proportion were observed at 48 d

and 60 d (Table 2.2). C. formosanus were able to sustain high numbers of soldiers

corresponding to the increase of temperature. At 48 d, the mean survival was

significantly higher at 30 °C than at temperatures of 20 °C or 25 °C, although termites

with a proportion of 20% or more soldiers exhibited a lower rate of survival (Figure

2.3-A). Furthermore, survival rates significantly increased with the increase of soldier

proportion until a 30% soldier proportion at 33 °C (Figure 2.3-A). At 60 d, termite

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Table 2.2. Effects of temperature and soldier proportion on survival of C. formosanus at different observational times.

Obs.* Sources d f Mean F P of variation square 12 d Temperature 3 0.84 22.090.0001 Soldier proportion 4 0.12 5.62 0.0005 Temperature x soldier proportion 12 0.05 1.23 0.2754 24 d Temperature 3 0.81 25.0 0.0001 Soldier proportion 4 0.98 30.11 0.0001 Temperature x soldier proportion 12 0.06 1.74 0.0744 36 d Temperature 3 0.7 13.60 0.0001 Soldier proportion 4 1.14 22.16 0.0001 Temperature x soldier proportion 12 0.07 1.37 0.1978 48 d Temperature 3 1.27 46.0 0.0001 Soldier proportion 4 0.35 12.7 0.0001 Temperature x soldier proportion 12 0.12 4.22 0.0001 60 d Temperature 3 0.32 7.19 0.0001 Soldier proportion 4 1.14 25.63 0.0001 Temperature x soldier proportion 12 0.11 2.67 0.0436

* Day of observation.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. i IS25 C IS25 u 33 □ □ 20 C 20 □ at temperatures of treatments four cohorts under 36 Day of observation of Day C. formosanus C. five observational times. Means separated by different letters indicate significant differences using Tukey- Tukey- using differences significant indicate different letters by separated times. Means observational five Kramer HSD procedure. HSD Kramer Figure 2.1. Mean survival and SEM of and SEM survival 2.1. Mean Figure « 30 O O 50 c 4*>

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 60 48 under five initial soldier proportions at five at five proportions soldier initial five under □30% soldiers 140% soldiers soldiers □30% 36 j H 0% soldiers □ 10% soldiers □ 20% soldiers soldiers 20% □ soldiers soldiers 10% □ 0% H j T j r h b Day ofobservation C. formosanus C. 24 * 12 Kramer HSD procedure. HSD Kramer Figure 2.2. Mean survival and SEM of SEM and survival Mean 2.2. Figure observational times. Means separated by different letters indicate significant differences using Tukey- Tukey- using differences significant indicate letters different by separated Means times. observational a a 0 10 90 80 20 60 40 100 tn o O O 50 a b 70 \ 0 I 30 j* <4H I/I Ul

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. survival did not decline significantly until soldier proportions exceeded 40% at 30 °C

and 33 °C. However, at 20 °C and 25 °C, survival rates declined significantly when

soldier proportions exceeded 20% (Figure 2.3-B).

There was a significant increase of soldier and pre-soldier production with

increasing observational times when the soldier proportion was 0% (R2=0.7224 at

25 °C, pO.OOOl; R2=0.832 at 30 °C, p<0.0001; R2=0.6037 at 33 °C, p<0.0001), except

at a temperature of 20 °C where there were no soldiers or pre-soldiers produced (Figure

2.4-A). Termite cohorts at a temperature of 30 °C produced a higher soldier proportion

than those at 20, 25, or 33 °C when initial soldier proportions were 0 up to 10%

(Figures 2.4-A, 2.4-B).

Temperature and initial soldier proportion on consumption. There was no

significant effect of temperature by initial soldier proportion on wood consumption

rates for any observation times (p=0.0826 at 12 d, p=0.2171 at 24 d, p=0.1662 at 36 d,

p=0.3277 at 48 d, p=0.3146 at 60 d). Wood consumption rates increased significantly

with rising temperature, up to 30 °C (Figure 2.5). At 20 °C, termites showed the lowest

consumption rate (Figure 2.5). Consumption rates significantly increased with increased

soldier proportions at observations 36 d and 48 d (Figure 2.6). Consumption rate was

not significantly affected by the soldier proportions at 12 d, 24 d, or 60 d (Figure 2.6).

Discussion

Survival and wood consumption in the Formosan subterranean termite changed

significantly in response to different temperatures and initial soldier proportions. The

highest survival and consumption rates were at 30 °C (Figure 2.1, Figure 2.5),

suggesting that this temperature is optimal. Mannesmann (1972) reported that the

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 2.3rA □ 0% soldiers OD10% soldiers □ 20% soldiers □ 30% soldiers H40% soldiers

20 25 30 33 Temperature (#C)

2.3-B □ 0% soldiers ■ 10% soldiers ■ 20% soldiers ■ 30% soldiers B40% soldiers

20 25 30 33 Temperature (*C)

Figure 2.3 (A-B). Mean survival and SEM of C. formosanus at different temperatures and soldier proportions on 48 d (2.3-A) and 60 d (2.3-B). Means separated by different letters indicate significant differences using Tukey-Kramer HSD procedure.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. without prohibited reproduction Further owner. copyright the of permission with Reproduced Figure 2.4 (A-B). Mean proportion and SEM of soldiers in in soldiers of SEM and proportion Mean (A-B). 2.4 Figure Mean proportion of soldiers at test Mean proportion of soldiers at test termination (%) termination (%) B: Initial soldier proportion (10%) proportion soldier Initial B: 20 25 10 15 20 0 5 A: Initial soldier proportion (0%) proportion soldier Initial A: 2 4 6 8 60 48 36 24 12 12 ; r ; Day of observation of Day Day o f observation f observation o Day 58 25 *C 25 4824 .fr osanus. C. form 30 30 *C 33 *C 25 25 *C *C 0 2 6036 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. without prohibited reproduction Further owner. copyright the of permission with Reproduced o o

□ □ 20°C □25°C 3/pooAv Sui) co 535323232389485391235353484823234848235348485353485323484823535353532323 m o si 33( 235323234889904823234848234853482348232323484823484823484853 jom (Xep/sd)iuu3) •**■o Xq ajRi uoqduinsuoo UEap\ XqajRi uoqduinsuoo co o i o S W W ‘ S « % » > » S V « W V f N » N » ■\■ _ “ ■ ■ ■ » ■ % ■ % ■ % ■ » » % ■ ■ % _ % » % ■%■ . / / / / / / / / / / / / / * 59 %»s ^•_% ^ ■% ■_% s «.S ■ » s s « s »% » A / / / / / / / / / / / ' • s * s » s • % • % ■ % • s • * ■ » v • s« % »\ • CM o ltii>iiEi!ii!lii!hi!ii •_** •_*» •_' CM OJ co co CO CO O C .O Q _o m 69 v > o o C/3o £ eo c 8 E N O CN ^ s « .2 .5 c c .5 J ^ - « « o « “ § ! a 8 00 A I C

23234853535353232353534823482348235348534853232323 60 40% soldiers □ soldiers 0% ■ soldiers 10% □ soldiers 20% B soldiers 30% 4 48 Means proportions. soldier at five C. formosanus C. 36 Day of observation of Day 234848535348484848235353534848532348234848892323234848 24 4853232323532353234848232323482323235323482323532348484848235353484853 12 Figure 2.6. Mean consumption rate and SEM in and SEM rate consumption 2.6. Mean Figure separated by different letters indicate significant differences using Tukey-Kramer HSD procedure. HSD Tukey-Kramer using differences significant indicate different letters by separated •e u 30 0\ ©

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. protozoa of the hindgut had different reactions to different temperatures in the

Formosan subterranean termite. Suppression of the protozoa in C. formosanus causes a

significant decrease in wood consumption rate and termite survivorship (Delaplane &

La Fage 1989). As present results indicate, the temperature of 30 °C may also provide

an optimal temperature to the symbiotic protozoa in the Formosan subterranean

termite.

On average, C. formosanus showed a significantly higher survival rate when

soldier proportions were <20% (Figure 2.2). The relationship between increasing

temperatures and soldier proportion suggests that the optimal soldier proportion is not

the maximum supportable soldier proportion. Optimality is dynamic and depends on

temperature. Soldier proportions also vary by termite species. R. virginicus workers do

not sustain soldiers in excess of 20% (Oi 1994). In contrast, C. formosanus can

survive at much higher soldier proportions; up to 48% (Haverty 1979, Haverty et al.

1989). Su and La Fage (1987) demonstrated that C. formosanus soldiers were

cannibalized by workers when soldier proportions were > 50%, suggesting that food

availability may be an important factor affecting fluctuations in soldier proportions.

The evidence from this study indicates that increased temperatures may trigger soldier

differentiation through increased food consumption (Figure 2.5). It is well established

that juvenile hormone promotes soldier differentiation in termites (Yin & Gillot 1975).

The increased food consumption may influence juvenile hormone titres that promote

soldier differentiation.

There were no soldiers and pre-soldiers in C. formosanus observed when units

were exposed to 20 °C. Temperatures suppress soldier differentiation in the Formosan

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. subterranean termite. Soldiers are produced when their proportions fall below normal

levels (Haverty 1979). Luscher (1961, 1972) suggested that the production of soldiers

might be suppressed by a primer pheromone produced by existing members of this

caste. Nutrition and other environmental factors also have a strong influence on caste

determination (Esenther 1970, Lenz 1994, Henderson 1998). Based on the present

study, a temperature below 20 °C inhibits soldier differentiation in the Formosan

subterranean termite. Perhaps this is due to the presence and maintenance of a certain

levels of primer pheromone produced by workers.

Insect growth regulators (IGRs), either juvenile hormone analogs or mimics and

chitin synthesis inhibitors, have been widely investigated as active ingredients to

control subterranean termites (Haverty et al. 1989, Su & Scheffrahn 1989, Su 1994,

Jones 1984, 1989, Oi 1994, Henderson & Forschler 1996). The testing sites, feeding

periods, and the ability of termites to choose a food source in a field environment are

important factors that can affect the feasibility of using IGRs in termite control.

According to Oi (1994), continuous feeding for a long period (>4 wk) is required to

reach a high soldier proportion (> 20%) for effectively controlling Reticulitermes spp.

using pyriproxyfen. The results from this study indicate that effects of temperature and

soldier proportion on termite survival are significant, suggesting that the interaction of

testing time by temperature by soldier proportion may present an additional obstacle

for field evaluation of juvenile hormone analogs or mimics. The Formosan

subterranean termite is able to support high soldier proportion with increased

temperatures without colony demise.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. References

Chu, H. -H., T. -D. Tai, T. -F. Chen and M. W. King. 1974. Induction of soldier differentiation in the termite, Reticulitermes Jlaviceps Oshima with juvenile hormone analogues. Acta. Entomol. Sinica. 17:161-165 (in Chinese with English abstract).

Delaplane, K. S. and J. P. La Fage. 1989. Suppression o f termite feeding and symbiotic protozoans by the dye, Sudan Red 7B. Entomol. Exp. Appl. 50:265-270.

Delaplane, K. S., A. M. Saxton and J. P. La Fage. 1991. Foraging phenology of the Formosan subterranean termite (Isoptera: Rhinotermitidae) in Louisiana. Am. Midi. Nat. 125.

Esenther, G. R. 1977. Fluctuation of survival, growth, and differentiation in biweekly samples of Reticulitermes flavipes workers. Mater, und Org. 12:49-58.

Gay, F. J., T. Greaves, F. G. Holdaway and A. H. Wetherly. 1955. Standard laboratory colonies of termites for evaluating the resistance of timber, timber preservatives, and other materials to termite attack. Aust. Commonw. Sci. Ind. Res. Org. Bull. p. 277.

Haverty, M. I. 1977. The proportion of soldiers in termite colonies: a list and a bibliography. Sociobiology. 2:199- 216.

Haverty, M. I. 1979. Soldier production and maintenance of soldier proportions in laboratory experimental groups of Coptotermes formosanus Shiraki (Isoptera: Rhinotermitidae). Ins. Soc. 26:69-84.

Haverty, M. I. and R. W. Howard. 1979. Effects of insect growth regulators on subterranean termites: induction of differentiation, defaunation, and starvation. Ann. Entomol. Soc. Am. 72:503-508.

Haverty, M. I. and R. W. Howard. 1981. Production of soldiers and maintenance o f soldier proportions by laboratory experimental groups of Reticulitermes flavipes (Kollar) and Reticulitermes virginicus (Banks) (Isoptera: Rhinotermitidae). Ins. Soc. 28:32-39.

Haverty, M. I. and W. J. Nutting. 1974. Natural wood-consumption rates and survival of a dry-wood and a subterranean termite at constant temperatures. Ann. Entomol. Soc. Am. 67: 153-157.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Haverty, M., N. -Y. Su, M. Tamashiro and R. Yamamoto. 1989. Concentration- dependent pre-soldier induction and feeding deterrency: potential of two insect growth regulators for remedial control of the Formosan subterranean termite (Isoptera: Rhinotermitidae). J. Econ. Entomol. 82:1370-1374.

Henderson, G. 1998. Primer pheromones and possible soldier caste influence on the evolution o f sociality in lower termites. In: Pheromone Communication in Social Insects, pp. 314-330. Vander Meer, R., M. D. Breed, M. L. Winston and K. E. Espelie (eds.). Westview press, Colorado, Oxford.

Henderson, G. and B. T. Forschler. 1996. Termite bait screening using naturally infested trees. In: Proc. 2nd Inter. Conf. Insect Pests in the Urban Environ, pp. 449-458. Wildey, K. B. (ed.). Heroit-Watt Univ., Edinburgh, Scotland.

Howard, R. W. and M. I. Haverty. 1981. Seasonal variation in caste proportions of field colonies of Reticulitermes flavipes (Kollar). Environ. Entomol. 10:546-549.

Hrdy, I. and J. Krecek. 1972. Development of superfluous soldiers induced by juvenile hormone analogues in the termite, Reticulitermes lucifugus santonensis. Ins. Soc. 19:105-109.

Jones, S. C. 1984. Evaluation of two insect growth regulators for the bait-block method of subterranean termite (Isoptera: Rhinotermitidae) control. J. Econ. Entomol. 77:1086-1091.

Jones, S. C. 1989. Field evaluation of fenoxycarb as a bait toxicant for subterranean termite control. Sociobiology. 15:33-41.

La Fage, J. P., N. -Y. Su, M. J. Jones and G. R. Esenther. 1983. A rapid method for collecting large number of subterranean termites from wood. Sociobiology. 7:305-309.

Lenz, M. 1994. Food resources, colony growth and caste development in wood- feeding termites. In: Nourishment and Evolution of Insects, pp. 159-210. Hunt, J. H. & C. A. Nalepa (eds.). Westview Press Inc., Boulder, Colorado.

Lenz, M. and E. R. Williams. 1980. Influence o f container, matrix volume and group size on survival and feeding activity in species of Coptotermes and Nasutitermes (Isoptera: Rhinotermitidae, Termitidae). Mater. & Org. 15: 25-46.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Lenz, M., R. A. Barrett and E. R. Williams. 1982. Influence of diet on the survival and wood consumption of Porotermes adamsoni (Froggatt) (Isoptera: Termopsidae) at different temperatures. Bull. Ent. Res. 72:423-435.

Luscher, M. 1961. Social control of polymorphism in termites. In :Insect Polymorphism, pp. 57-67. Kennedy, J. S. (ed.). Roy. Entomol. Soc., London.

Luscher, M. 1972. Environmental control o f juvenile hormone (JH) secretion and caste differentiation in the termites. Gen. and Comp. Endocrinol. Suppl. 3:509-514.

Mannesmann, R. 1972. Temperature on hind gut flagellates of Coptotermes formosanus Shiraki and Reticulitermes virginicus (Banks). Mater. & Org. 7:205-214.

Nakajima, S., K. Shimizu and Y. Nakajima. 1964. Analytical studies on the vitality of colonies of the Formosan termite, Coptotermes formosanus Shiraki: II. Seasonal fluctuations on the external characters of the workers, the ratio of caste-number and carbon dioxide in the nest of a colony. Miyazaki Univer., Faculty Agric. Bull. 9:222-227.

Oi, F. M. 1994. Foraging and colony dynamics of Reticulitermes spp. (Isoptera: Rhinotermitidae) in Gainesville, Florida. PhD Dissertation, Department of Entomology and Nematology, University of Florida, pp. 172.

Rencher, A. C. 1995. Methods of multivariate analysis. John Wiley & Sons, Inc. New York. pp. 174-271.

SAS Institute. 1989. SAS user’s guide: statistics. SAS Institute Inc. Cary, NC.

Su, N. -Y. 1994. Field evaluation of a hexaflumuron bait for population suppression o f subterranean termites (Isoptera: Rhinotermitidae). J. Econ. Entomol. 87:389-397.

Su, N. -Y. and J. P. La Fage. 1984. Comparison of laboratory methods for estimating wood consumption of Coptotermes formosanus (Isoptera: Rhinotermitidae). Ann. Entomol. Soc. Am. 77:125-129.

Su, N. -Y. and J. P. La Fage. 1986. Effects o f starvation on survival and maintenance of soldier proportion in laboratory groups of the Formosan subterranean termite Coptotermes formosanus (Isoptera: Rhinotermitidae). Ann. Entomol. Soc. Am. 79:312-316.

Su, N. -Y. and J. P. La Fage. 1987. Effects o f soldier proportion on the wood- consumption rate of the Formosan subterranean termite (Isoptera: Rhinotermitidae). Sociobiology. 13:145-151.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Su, N. -Y. and R. H. Scheffrahn. 1989. Comparative effects o f an insect growth regulator, S-31183, against the Formosan subterranean termite and the eastern subterranean termite (Isoptera: Rhinotermitidae). J. Econ. Entomol. 82:1125- 1129.

Su, N. -Y. and R. H. Scheffrahn. 1990. Potential of insect growth regulators as termiticides: a review. Sociobiology. 17:313-327.

Waller, D. A. and J. P. La Fage. 1987. Seasonal patterns in foraging groups of Coptotermes formosanus (Rhinotermitdae). Sociobiology. 13:173-181.

Waller, D. A. and J. P. La Fage. 1988. Environmental influence on solider differentiation in Coptotermes formosanus Shiraki (Isoptera: Rhinotermitdae). Ins. Soc. 35:144-152.

Wanyonyi, K. 1974. The influence of juvenile hormone analogue ZR 512 (Zoecon) on caste development in Zootermopsis nevadensis (Hagen) (Isoptera). Ins. Soc. 21:35-44.

Yin, C. -M. and C. Gillot. 1975. Endocrine control of caste differentiation in Zootermopsis angusticollis Hagen (Isoptera). Can. J. Zool. 53:1701-1708.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER IV

EFFECTS OF WOOD VOLUME AND SURFACE AREA ON WOOD CONSUMPTION RATE AND TERMITE SURVIVAL BY THE FORMOSAN SUBTERRANEAN TERMITE, COPTOTERMES FORMOSANUS SHIRAKI (ISOPTERA: RHINOTERMITIDAE) IN THE LABORATORY

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Introduction

Wood consumption rate and termite survival in laboratory experiments are data

that can be used to assess the resistance of timber (Lenz et al. 1984), chemically

treated wood products (Lenz & Williams 1980) and bait technology (Oi 1994).

However, consumption rates are affected by a multitude of factors (Howick 1975,

Delaplane 1991, Lenz 1994). These factors include the colony origin (Su & La Fage

1984a, Lenz 1994) and population density (Esenther 1985, Lenz & Williams 1980,

Lenz et al. 1984, chapter IV in this thesis). Some other factors also have important

impacts on termite survival, such as temperature (Haverty & Nutting 1974, Lenz et al.

1982, chapter II in this thesis), moisture (Delaplane & La Fage 1989a), feeding

materials (Smythe & Carter 1970, Behr et al. 1972, Howard & Haverty 1979, Su &

Tamashiro 1983), previous damage by conspecifics (Delaplane & La Fage, 1989b),

and experiment duration (Su & La Fage 1984b). A most fascinating discovery was that

a larger wood supply could trigger higher levels of wood consumption by termites

(reviewed by Lenz 1994, Hedlund & Henderson 1999). Akhtar and Jabeen (1981)

reported that the consumption rate difference was 6.6 times in Coptotermes heimi

(Froggatt) when feeding on the smallest versus the largest wooden blocks. In

Reticulitermes flavipes (Kollar), wood feeding rate differed by about 200 % when

termites were kept on a wood block of only 24 cm^ compared to one of 192 cm^

(Lenz 1994). Collins (1981) provided evidence from the field that, rather than feeding

at a constant rate, colonies adjusted their wood feeding in response to the food source

size. In addition, different volumes of wood appeared to affect the termite survival,

colony growth, and caste development. It was reported that foragers of R. flavipes

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. showed increased survival on larger wood blocks (Lenz 1994). However, in some

termite species, such as Coptotermes cynocephalus Holmgren, colony growth did not

appear to be positively correlated with increased wood size (Lenz 1994).

In laboratory studies, consumption rates are highly variable for C. formosanus

when fed on Pinus sp. (Delaplane 1991). Consumption rates ranging from 45mg wood

eaten /g termite / day to 114mg wood eaten / g termite / day have been recorded

(Delaplane 1991). According to Hedlund and Henderson (1999), C. formosanus

consumed more wood as wood mass increased in a feeding chamber, suggesting that

they mediate their feeding activity in response to available food size. However, it is

unclear how changing wood surface area can affect feeding rates and termite survival

when a constant volume of wood block is provided. Previous experiments in

Coptotermes heimi (Froggatt), Nasutitermes exitiosus (Hill), and R. flavipes indicated

that consumption rates increased considerably with the increased wood size (Lenz

1994). However, it was not determined whether wood consumption rates correspond

to continuously increasing wood volume or wood surface area. It is hypothesized that

C. formosanus will maintain equivalent consumption and survival rates regardless of

the wood surface area or wood volume provided. This hypothesis was tested in the

laboratory using wood blocks with different volumes and surface areas.

Materials and Methods

Termites. Two carton nests (colony I and colony II) of C. formosanus were

collected from infested trees in New Orleans in December 1996 and March 1997,

Louisiana. Colony I was a mature colony containing a large number of nymphs.

Colony II was a relatively young colony, the primary queen collected was only 2cm

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. in length and no nymphs were found in the nest. Termites were held in 250-liter cans

with pine as a food source and kept at 24-26 °C. Moistened corrugated cardboard rolls

were used to retrieve termites from the cans (La Fage et al. 1983). Termites were

gently knocked from the cardboard rolls into clean plastic trays (20cm diam., 20cm

height, Tristate Plastics, Inc., Dixon, Kentucky) and isolated from debris by allowing

them to cling to sheets o f moistened paper towels (Gay et al. 1955). In colony I, the

mean worker weight was 3.37 ± 0.13 (SD) mg. In colony II, the mean worker weight

was 3.23 ± 0.07 (SD) mg. Consumption rate was calculated as mg eaten wood / g

worker / day (Haverty & Nutting 1974, Su & La Fage 1984b).

Experimental design. A completely randomized design blocked on the two

colonies was conducted. Ten treatments (5 wood volume x 2 surface area) were

evaluated, which were comprised of wood blocks with five different volumes and two

different surface areas corresponding to each wood volume (Table 3.1). Wood

consumption rate, survival of workers and soldier proportion were examined for each

treatment. All wood blocks were oven-dried at 85 °C for 56 h, then weighed and

treated by individually soaking them in deionized distilled water for 5 h before testing.

Assay arena and data collection. Glass screw-top jars (10cm diam.x 20cm high,

Altrista Corporation, Muncie, Indiana) were used as testing containers. All wood

blocks were cut using a table saw from a single board (Pinus sp.) that was free of

knots. Three hundred termites with 15 % soldiers were placed in each glass screw-

top jar. In addition to termites, each jar received 590g of acetone-washed, oven-dried

sand moistened with 125ml o f deionized distilled water. All jars were kept in a

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 10.8 6.8 S|-S2 (cm^) colonies. colonies. Surface C. formosanus C. Surface area II (S2> cm2) (S2> area II Surface [(7x6)+(7x2)+(6x2)]x2 = 136 18 [(7x2)+(7x3.6)+(2x3.6)]x2 92.8 = Surface area I (Sj^ cm2) (Sj^ area I Surface ) nested within each level (V). of wood volume level within each nested ) 2 [(3.6x3.5)+(3.6x2)+(3.5x2)]x2=53.6 Sj: 60.4 = 1.8)]x2 1.8)+(2x [(7x2)+(7x [(3.6x3.5)+(3.6x4)+(3.5x4)]x2= 82 Sh: [(6x3.5)+(6x4)+(3.5x4)]x2 = 118 Sf [(7x4)+(7x4)+(4x4)]x2 = 144 Srf: [(8x7)+(8x2)+(7x2)]x2 = 172 28 [(7x5)+(7x4)+(5x4)]x2 = 166 Sb: [(10x7)+(10x2)+(7x2)]x2= 208 42 7x2x1.8 =25.2 7x2x3.6 =50.4 8x7x2 =112 7x6x2 = 84 10x7x2 10x7x2 =140 V5: 3.6x3.5x2 V5: 25.2 = Sj: V4: 3.6x3.5x4V4: = 50.4 Sg: V3: 6x3.5x4V3: = 84 Se: Wood volume (cm^) volume Wood V2: 7x4x4 =112 Sc: area I (Sj) and surface area 11 (S (Sj)I area area 11 surface and Vj: 7x5x4 =140 Sa: Table 3.1. Differences in wood volume and surface area with different wood blocks two blocks differentfor wood with area and surface volume wood in Table 3.1. Differences

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. bioclimatic chamber at 27 ± 0.1 °C. At the start of the experiment, a wood block was

put into each test unit. A total of 100 experimental units were used in this experiment

(10 treatments x 2 colonies x 5 replicates). On day 50, experimental units were

dismantled. Wood blocks were cleaned, oven-dried at 85 °C for 56 h, and re-weighed

to determine the consumption of each wood block. Surviving workers and soldiers

were counted.

Data analysis. The consumption rate, percent survival of workers, and soldier

proportion were transformed with arcsine square root to create homogeneous

variances. Data were back-transformed for presentation purposes. The effect of

different wood volumes and surface areas on consumption rates was determined by a

mixed model analysis of variance (SAS Institute 1989, Littell et al. 1996). If the

ANOVA was significant, Tukey’s studentized range test was conducted to check for

differences in wood consumption rate corresponding to the different volumes and

surface areas (SAS Institute 1988). ANOVA was also used to evaluate the effect of

different wood volumes and surface areas on consumption rate after adjustment for

termite survival (SAS Institute 1989). The number of workers and soldiers were

counted simultaneously on each experimental unit. Typically, these variables were

correlated. Therefore, the effect of wood volume and surface areas on survival of

workers and soldier proportion at the test termination was tested by a multivariate

ANOVA (Rencher 1995) followed by a univariate F-test on each variable and Tukey’s

studentized range test for equal sample size, if ANOVA was significant. An alpha

level of 0.05 was used to determine significant differences for all statistical tests.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Results

Consumption rate. Wood consumption rate significantly increased with the

increase in wood volume for both colonies (F=21.24, df=4,4; p<0.0059; Figures 3.1,

3.2). Results of multiple comparisons of means indicated that as available wood

surface area increased, wood consumption rate did not show a significant increase or

decrease within wood blocks of the same volume (Table 3.2).

On average, C. formosanus in colony II consumed a significantly greater amount

of wood than colony I (F=14.11, df=l,4; p<0.0199). Mean wood consumption rates (±

SD) were 62.9 ± 16.9mg wood /g termites / day for colony II and 50.4 ± 1 1 .6mg wood

/g termites / day for colony I. However, both colony I and colony II showed the same

trends in response to wood consumption rates on wood blocks with different wood

volumes and wood surface areas. There was no colony by wood volume effect

(F=2.13, df=4,5; p=0.2249) or colony by wood surface area effect (F=0.32, df=5, 80;

p=0.8939). Wood consumption rate increased significantly in colony I from 25.2 to

84.0cm3 and from 50.4 to 140.0cm^ of wood volumes (Figure 3.1). In colony II, a

significant increase of wood consumption rate occurred at wood volumes >84.0cm^

(Figure 3.2).

The Formosan subterranean termite consumed a significantly greater amount of

wood as available wood volume increased (with adjustment for termite survival) at the

termination of the test (Table 3.3). The effect of wood surface area was not significant

(Table 3.3). Effects of termite colony by wood volume and colony by wood surface

Area were also evaluated and were not be significant. Both colony I and colony n

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. wood in ranging sp., Pinus >! J-ii >! [Ax. I” • - - I” • -r n imm !■-. -ij vfi-. of on blocks ’11 vi •j -;i iAv'-J iAv'-J -;i •j i-'U.-T I’.’!* i-'U.-T [1 l \ Ul 'I t e a C. formosanus C. Wood volume (cm3) volume Wood 25.2 25.2 50.4 84 112 140 Colony 1 Colony o 10 30 20 40 70 60 50 volume from 25.2 to 140cm3. Means with the same letter are not significantly different using Tukey's Tukey's using different significantly are not the same with letter Means to 25.2 volume from 140cm3. Figure 3.1. Mean consumption rate and SEM by rate and SEM consumption Mean 3.1. Figure studentized test. studentized range c o o o * 00 a u a a o 00 a •13 U £ •o T3

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 140 sp., ranging Pinus 112 of onblocks C. formosanus C. 84 Wood volume (cm3) volume Wood 25.2 50.4 Colony Colony II Figure 3.2. Mean consumption rate and SEM by SEM and consumption rate 3.2. Mean Figure different significantly not are with letter the same Means to 25.2 wood volume in from 140cm3. range test. studentized Tukey's using 8 O c 3 oo oo o a E 0 1 e

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Table 3.2. Results for testing the equivalent consumption rate (± SEM) by C. formosanus at different wood surface areas when equivalent wood volume was provided using Tukey’s studentized range tests.

Colony Volume Surface area Consumption rate Ho p-value I Vl sa 36.5 ± 2.9 Sa=Sb 1.000 Sb 4 1.3 ± 0.7 V2 Sc 42.3 ± 0.9 Sc=Sd 1.000 Sd 46.2 ± 2.8 V3 Se 45.7± 1.0 Se=Sf 1.000 Sf 56.1 ±3.5 V4 Sg 50.9 ± 7.7 Sg=Sh 1.000 Sh 55.7 ± 4.0 V5 Si 55.1 ±2.2 Si=Sj 1.000 SJ 57.6 ± 2.2

II Vl Sa 38.2 ±3.3 Sa=Sb 1.000 Sb 46.1 ±4.9 V2 Sc 4 1.3 ± 4.7 Sc- S(i 1.000 Sd 52.0 ± 4.7 V3 Se 55.4 ± 5.4 Se=Sf 1.000 Sf 58.8 ±2.7 V4 Sg 61.9 ±5.6 Sg=Sh 1.000 Sh 60.6 ± 11.4 V5 Si 65.8 ± 10.3 Si=Sj 1.000 Sj 68.9 ± 3.0

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. showed the same trends in wood consumption rates when adjustment for termite

survival was taken into account (Table 3.3).

Table 3.3. Effects of wood volume and wood surface area on wood consumption rate (x) with adjustment for termite survival at the test termination.

Sources of variation d f Mean square F P

Colony 1 0.43 6.26 0.0144

Volume 4 0.70 9.94 0.0001

Surface area 5 0.15 2.11 0.0906

Colony by volume 4 0.08 1.23 0.304

Colony by surface area5 0.07 1.08 0.3781

Termite survival. There was no colony effect on worker survival (F=4.56, df=l,

4; p=0.0994). The mean percent survival of workers showed a significant increase in the

largest wood block as compared with other wood blocks (Table 3.4, Figures 3.3, 3.4).

However, the soldier proportion showed a considerable decrease on wood blocks having

the largest wood volume (Table 3.4). Furthermore, there was no significant influence of

wood surface area on worker survival and soldier proportion (Wilks’?i=0.97, F=0.54,

df=5, 80; p=0.7684). Mean survival rate (± SD) of workers was 64.0 ± 4.9 % in colony I

and 64.8 ± 4.6 % in colony II (Figures 3.3, 3.4).

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. sp., 140 175 Pinus on blocks of 112 170.4 170.4 169.8 C. formosanus C. 162:2 84 162 Colony I: Wood volume (cm3) 137 □ area Surface 50.4 166.6 25.2 □ area Surface I 145.8152.8 ranging in woodin ranging volume 25.2 from to 140cm3. Figure 3.3. Mean number of workers and SEM SEM in and of workers 3.3. Figure number Mean 120 160 180 200 £ £ 0 5 80 o u 100 1 G C3 $3 $3 140 I 60 *

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. sp., 187.8 140 Pinus 165.6 187.2 on blocks of 112 166.8 C. formosanus C. 84 155.4165.0 □Surface area C olony II: W ood volum e (cm 3) 154.8 50.4 170.2 161.8 □Surface area I 25.2 145.4 Figure 3.4. Mean number ofworkers and SEM in ranging in wood volume from 25.2 to 140cm3. 250 200 150 % O c 100 & CO c 0> I s

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Table 3.4. Mean percent survival of workers and mean soldier proportion (% ± SEM) in C. formosanus for both colonies. Means with the same letter are not significantly different using Tukey’s studentized range test.

Volume Percent survival N Soldier proportion N of worker

Vl 83.6 ± 0.6 a 20 16.4 ±0.6 a 20 v 2 83.6 ±0.7 a 20 16.4 ±0.6 a 20

V3 85.4 ± 1.0 ab 20 14.6 ± 1.1 ab 20

V4 84.3 ± 0.5 ab 20 15.3 ± 0.5 ab 20

V5 86.4 ± 0.7 b 20 13.6 ± 0.6 b 20

Discussion

Workers of Formosan subterranean termites clearly consumed greater amounts of

wood as available wood volume increased. However, wood consumption rate was not

significantly higher in wood blocks with larger surface given a constant volume of

wood blocks. This result supports findings by Hedlund and Henderson (1999), who

showed a positive trend in termite survival and wood consumption by Formosan

subterranean termites as wood mass increased in the feeding chamber. However, data

from the present study provide new quantitative information about how wood volume

and wood surface area affect wood consumption and survival in the Formosan

subterranean termite. The result supports the hypothesis that changeable wood surface

areas had no significant influence on wood consumption rate and termite survival.

Several factors might be used to interpret the apparent behavioral modification of

feeding in response to available food size by C. formosanus. First, termites may be

able to discriminate high quality wood by large volume. C. formosanus had been

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. reported to make more penetrating tunnels and fewer exterior excavations than

Reticulitermes species (Delaplane 1991). Larger exterior surface areas do not

guarantee an effective channelization by C. formosanus. Second, modification may

result in a colony level "decision" where termites make more food available for brood

production and regulation of caste proportions on a large wood volume. Termites may

use several means to assess the volume of a food source available, as suggested by

Lenz (1994). Termites may assess the volume of food available by walking over it or

generating and perceiving acoustic signals and deriving information from these signals

about their food source (Lenz 1994). Seeley (1977) observed that the honey bee ( Apis

mellifera L.) measures nest cavity volume by walking across the surface. Haack et al.

(19S8) reported that some wood-boring insects may use ultrasonic acoustical

emissions to perceive their food source. In fact, acoustic signals are used by

Microcerotermes crassus Snyder for some forms of communication within a colony

(Kny 1982). Acoustic signals are generated only when termites bite into wood (Fujii et

al. 1990), suggesting that the generation of acoustic signals may be independent of

wood surface area. Hedlund and Henderson (1999) suggested that termites of C.

formosanus may use chemical signals from labial gland secretions to detect the food

size. Reinhard and Kaib (1995) reported that the African termite, Schedorhinotermes

lamanianus (Sjostedt) used the labial gland secretion to stimulate gnawing at the

secretion site. Labial gland secretions may be used to detect wood volume and surface

area. However, present results could exclude the possibility that termites respond to

large food sources by cues on wood exterior surface because wood blocks with large

surface areas did not support higher consumption rates. In the drywood termite

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Cryptotermes, neotenic production was highest on the largest wood blocks, however,

termites did not even move over the outer surface of wood blocks at the end of

experiment, suggesting that termites feed on wood without obtaining surface area

information (Lenz 1994).

Termites exploit food sources that have relatively low nutritive value (Waller & La

Fage 1987). Consequently, energetic costs which are associated with the limited

nutrition of wood may be important regulators of feeding behavior. In two laboratory

choice tests, Delaplane (1991) reported that Formosan subterranean termites prefer

wood blocks with high moisture and prefer a particular wood block when feeding

damage has occurred on otherwise equivalent wood blocks. Delaplane (1989c)

suggested that it would be advantageous to termites to excavate wood, dig tunnels, and

lay pheromonal trails in a particular wood block. This may be a strategy of energetic

savings by termites. Larger wood volume may provide advantages in the maintenance

of high moisture of wood, the transfer of trail pheromone, and the development of

interior galleries in wood blocks with minimum energy expenditure.

References

Akhtar, E. S. and M. Jabeen. 1981. Influence o f specimen size on the amount o f wood consumed by termites. Pakistan J. Zool. 13:79-84.

Behr, E. A., C. T. Behr and L. F. Wilson. 1972. Influence of wood hardness on feeding by the eastern subterranean termite Reticulitermes flavipes (Isoptera: Rhinotermitidae). Ann. Entomol. Soc. Am. 65:457-460.

Collins, N. M. 1981. Consumption of wood by artificially isolated colonies of the fungus-growing termite Macrotermes bellicosus. Entomologia Experimental et. Applicata. 29:313-320.

Delaplane, K. S. 1991. Foraging and feeding behaviors o f the Formosan subterranean termite (Isoptera: Rhinotermitidae). Sociobiology. 19:101-114.

Delaplane, K. S. and J. P. La Fage. 1989b. Preference o f the Formosan subterranean termite (Isoptera: Rhinotermitidae) for wood damaged by conspecifics. J. Econ. Entomol. 82:95-100.

Delaplane, K. S. and J. P. La Fage. 1989c. Variance in feeding on equivalent wood blocks by the Formosan subterranean termite in laboratory choice tests. Sociobiology. 13:227-233.

Esenther, G. R. 1985. The density factor in the termite bioassays. The International Research Group on Wood Preservation Working Group. Document No: IRG / W P / 1252. p. 5.

Fujii, Y., M. Noguchi, Y. Imamura and M. Tokoro. 1990. Using acoustic emission monitoring to detect termite activity in wood. Forest Products J. 40:34-36.

Haack, R. A., R. W. Blank, F. T. Fink and W. J. Mattson. 1988. Ultrasonic acoustical emissions from sapwood of eastern white pine, northern red oak, red map, and paper birch: implications for bark- and wood-feeding insects. Florida Entomologist. 71:427-440.

Haverty, M. I. and W. J. Nutting. 1974. Natural wood-consumption rates and survival of a dry-wood and a subterranean termite at constant temperatures. Ann. Entomol. Soc. Am. 67:153-157.

Hedlund, J. C. and G. Henderson. 1999. Effects o f available food size on search tunnel formation by the Formosan subterranean termite (Isoptera: Rhinotermitidae). J. Econ. Entomol. 92:610-616.

Howard, R. W. and M. I. Haverty. 1979. Defaunation, mortality and soldier differentiation: concentration effects of methoprene in a termite. Sociobiology. 3:73-77.

Howick, C. D. 1975. Influence of specimen size, test period and matrix on the amounts of wood eaten by similar groups of laboratory termites. Proc. A. Conv. Br. Wood Preserv. Ass. 51-63.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. fCny, U. 1982. Acoustic conununication between Microcerotermes crassus Snyder. International Research Group on Wood Preservation, Stockholm, Sweden. Document No. IRG / WP / 1158. p. 5.

La Fage, J. P., N. -Y. Su, M. J. Jones and G. R. Esenther. 1983. A rapid method for collecting large number of subterranean termites from wood. Sociobiology. 7: 305-309.

Lenz, M. and E. R. Williams. 1980. Influence of container, matrix volume and group size on survival and feeding activity in species of Coptotermes and Nasutitermes (Isoptera: Rhinotermitidae, Termitidae). Mater. & Org. 15:25-46.

Lenz, M., R. A. Barrett and E. R. Williams. 1982. Influence o f diet on the survival and wood consumption o f Porotermes adamsoni (Froggatt) (Isoptera: Termopsidae) at different temperatures. Bull. Ent. Res. 72:423-435.

Lenz, M., R. A. Barrett and E. R. Williams. 1984. Implications for comparability of laboratory experiments revealed in studies on the effects of population density on vigor in Coptotermes lacteus (Froggatt) and Nasutitermes exitiosus (Hill) (Isoptera: Rhinotermitidae & Termitidae). Bull. Ent. Res. 74:477-485.

Littell, R. C., G. A. Milliken, G. A., Stroup, W. W. and R. D. Wolfmger. 1996. SAS system for mixed models. SAS Institute Inc., Cary, NC.

Oi, F. M. 1994. Foraging and colony dynamics of Reticulitermes spp. (Isoptera: Rhinotermitidae) in Gainesville, Florida. Ph.D. Dissertation, Department of Entomology, University of Florida, Florida. 172 pp.

Reinhard, J. and M. Kaib. 1995. Interaction of pheromones during food exploitation by the termite Schedorhinotermes lamanianus. Physiol. Entomol. 20:266-272.

Rencher, A. C. 1995. Methods of multivariate analysis. John Wiley & Sons, Inc., New York.

SAS Institute. 1989. SAS user’s guide: statistics. SAS Institute Inc., Cary, NC.

Seeley, T. 1977. Measurement of nest cavity volume by the honey bee ( Apis mellifera L.). Behav. Ecol. Sociobiol. 2:201-227.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Smythe, R. V. and F. L. Carter. 1970. Feeding responses to sound wood by Coptotermes formosanus, Reticulitermes flavipes, and R. virginicus (Isoptera: Rhinotermitidae). Ann. Entomol. Soc. Am. 63:841-847.

Su, N. -Y. and J. P. La Fage. 1984a. Differences in survival and feeding activity among colonies of the Formosan subterranean termite (Isoptera: Rhinotermitidae). Z. Ang. Ent. 97:134-138.

Su, N. -Y. and J. P. La Fage. 1984b. Comparison of laboratory methods for estimating wood consumption of Coptotermes formosanus (Isoptera: Rhinotermitidae). Ann. Entomol. Soc. Am. 77:125-129.

Su, N. -Y. and M. Tamashiro. 1983. Wood-consumption rate and survival of the Formosan subterranean termite (Isoptera: Rhinotermitidae) when fed one of six woods used commercially in Hawaii. Proc. Hawn. Entomol. Soc. 26:109-113.

Waller, D. A. and J. P. La Fage. 1987. Seasonal patterns in foraging groups o f Coptotermes formosanus (Rhinotermitdae). Sociobiology. 13:173-181.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER V

EFFECT OF TERMITE DENSITY ON WOOD CONSUMPTION AND TERMITE SURVIVAL BY THE FORMOSAN SUBTERRANEAN TERMITE, COPTOTERMES FORMOSANUS SHIRAKI (ISOPTERA: RHINOTERMITIDAE)

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Introduction

In social insects, intraspecific competition for limiting resources is known to

produce cooperative group living among diverse animal taxa (Wilson 1975). Traniello

(1983, 1989) suggested that such cooperation enables the ant, Lasius neoniger L. to

exploit valuable prey items more energetically. Termites might behave very differently

from ants, as suggested by Waller and La Fage (1987). Termites are thought to be

more self-sufficient than the social Hymenoptera due to their hemimetabolous

characteristics (Wheeler 1994).

It has been assumed that large termite groups are more vigorous than smaller ones

(Becker 1969). According to Delaplane and La Fage (1987), Formosan subterranean

termites concentrate feeding on a specific wood block even when other blocks were

present. There may be some energetic savings exploited by this behavior. For this

reason, the Formosanus subterranean termite, Coptotermes formosanus Shiraki may

maintain a high population density on a preferred wood.

In laboratory bioassay tests with termites, where the amount of wood eaten is

regarded as an important assessment criterion of termite vigor, the variation in termite

density may exert a significant influence. Previous information on Nasutitermes

exitiosus (Hill) (Lenz & Williams 1980), Coptotermes lacteus (Froggatt) (Howick

1975, 1978, Lenz et al. 1984), and Mastotermes darwiniensis Froggatt (Lenz et al.

1984) demonstrated a strong relationship between food consumption rate and termite

density. In the eastern subterranean termite, Reticulitermes flavipes (Kollar), the

termite growth, debris production, and consumption rate declined progressively as

termite density increased, but, the survival of termites was always high regardless

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. (Esenther 1985). Compared to other rhinotermitids, C. formosanus shows

conspicuously higher consumption rates on wood (Smythe & Carter 1970, Delap lane

& La Fage 1990). A comparative experiment indicated that C. formosanus made more

penetrating galleries than did Reticulitermes spp. in the laboratory (Delaplane & La

Fage 1990). However, laboratory consumption rates in the Formosan subterranean

termite vary widely when groups of termites are comprised of varying caste ratios (Su

& La Fage 1987, chapter II in this thesis) and temperature (chapter II in this thesis).

These findings served to guide a laboratory study to further evaluate the effect of

termite density on Formosan subterranean termite vigor, as measured by wood

consumption and termite survival.

Materials and Methods

Termites. C. formosanus from a single colony source was field collected from a

baldcypress tree (Taxodium distichum (L.) Rich.) in Sam Houston Jones State Park

along the Calcasieu River near Lake Charles, Louisiana. Termites were held in

containers (250 liter cans) containing moistened wood blocks and cardboard rolls at

24-28 °C for ca. six months before testing. Moistened corrugated cardboard rolls were

used to collect termites from the cans (La Fage et al. 1983). Termites were gently

knocked from the cardboard rolls into clean plastic containers (20cm diam., 20cm

height, Tristate Plastics, Inc., Dixon, Kentucky) and isolated from debris by allowing

them to cling to sheets of moistened paper towels (Gay et al. 1955). Termites were

weighed for calculation of wood consumption rate. Mean worker (± 0.01 mg) were

determined by weighing ten groups of 50 individuals.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Experimental design. A completely randomized design was performed to

measure wood consumption, termite survival, and soldier proportion of C.

formosanus on equivalent wood blocks (2.0 by 2.0 by 3.5cm). A pilot test indicated

that this size wood block was not fully consumed by 500 termites from the collected

colony in a 45-day test period at 26 °C. Termite densities were set up to 50, 100,

150,200, 250, 300, 350, 400, and 500 termites that consisted of nine treatments of

termite densities using undifferentiated larvae > the third instar. The soldier

proportion was 15% for each treatment. Termites were kept in glass screw-top jars

(4.5cm in diameter by 5.0cm high, * 65ml in space, Alltrista Corporation, Muncie,

Indiana). Each glass screw-top jar contained 20g of acetone-washed sand as a

foraging matrix (# 4 fine, Easy Crete Inc., Greenwell Springs, LA) moistened with

6ml of deionized distilled water. Wood blocks were oven dried for 56 h at 85 °C,

weighed (0.01 mg), and moistened up to five hours with deionized distilled water

before use. Each treatment of termite density was set up with six replicates. These

replicates consisted of 54 experimental units in total. All experimental units were

kept in a bioclimatic chamber at 26 ± 0.1 °C for a 45-day test period.

At the termination of testing, remnants of wood blocks were rinsed clean, oven-

dried as previously described, and re-weighed to determine the weight of each wood

block for consumption measurements. Numbers of workers and soldiers were

recounted. Consumption rate was calculated as mg eaten wood / g worker / day

(Haverty & Nutting 1974, Su & La Fage 1984).

Data analysis. Data were transformed by log (x) for the total consumption

amount and consumption rate and by arcsine square root for percent survival of

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. workers and soldier proportion to homogenize the variance. Data were back-

transformed for presentation purposes. Analysis of variance was performed using

SAS PROC GLM (SAS Institute 1989). The effect of termite density on survival of

termites and soldier proportion was tested by a multivariate ANOVA followed by a

univariate F-test on each variable (if ANOVA was significant). Tukey-Kramer HSD

procedure, with an alpha level of 0.05 was used to determine significant differences

between treatments (SAS Institute 1989). Regression analyses (PROC REG, SAS

Institute 1989) were conducted in a model with linear or linear and quadratic

coefficients to further evaluate the correlation between independent variables and the

observed increasing termite population density.

Results

Wood consumption. Wood consumption significantly increased as termite

density increased (F=193.04, df=8, 25; p<0.0001). Mean wood consumption increased

by 300mg for each treatment increase of 50 termites when the termite density was <

250. However, wood consumption did not significantly increase when the termite

density exceeded 300 termites (Table 4.1). The nonlinear regression showed a better

goodness of fit than that of the simple linear regression (Figure 4.1). A significant

quadratic relationship between termite density and wood consumption amount

(R2=0.99, p<0.0001) indicated that wood consumption amount did not increase when

termite density was greater than 300 (Figure 4.1).

During the 45-day test, the rate of wood consumption significantly decreased with

increasing termite density (F=23.16, df=8, 25; p<0.0001). However, the rate of wood

consumption was not significantly different with the termite density of 50 up to 300

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. (Table 4.1). A significant quadratic relationship was found, indicating that wood

consumption rate was significantly lower when termite density > 300 (Table 4.1,

Figure 4.2).

Termite survival and soldier proportion. Termite cohorts with densities > 350

had significantly higher mortality (Table 4.1, Figure 4.3). However, termite survival

did not significantly decrease when termite density was 350 or less (Table 4.1).

Similarly, there was a significant quadratic relationship between termite survival and

termite density (R.2=0.85, p<0.0001, Figure 4.3). The mean survival (± SEM) was

45.1 (± 6.4)% with the termite density of 500 and 84.0 (± 3.5)% with termite density

of 50. Soldier proportions varied significantly with changeable termite densities and

tended to linearly increase as available termite density increased (R.2=0.68, p<0.0067,

Figure 4.4).

Discussion

Examination of wood consumption and Formosan subterranean termite survival at

different population densities indicated that termite density significantly mediates

wood consumption and survival under the laboratory conditions. Mean wood

consumption rate and termite survival did not significantly increase or decrease at a

relatively low termite density, indicating that termite vigor was not affected. However,

when termite cohorts became crowded, i.e., densities exceeded 300-350, termite vigor

decreased rapidly. Howick (1975, 1978) and Lenz et al. (1984) found a similar pattern

of decreased termite vigor when termites were in crowded conditions. They results

indicated that C. lacteus and N. exitiosus exhibit feeding threshold densities (0.065

g/ml for the Australian species) above which the vigor of the termites decreased

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 15.0 ±3.2 15.0 ad 17.212.7 bd Mean soldier Mean 21.512.1 acde 22.5 ±4.122.5 be proportion 70.5 17.570.5 ab 22.612.0 eb 71.018.4 ab survival 80.014.6 a79.615.9 a 17.510.4 ab Mean percent percent Mean 37.713.9 cd 52.9110.6 be 21.512.6 eb 43.211.1 be 70.817.8 ab 25.215.1 eb 34.511.6d 45.116.4 c 26.011.4 ce 55.7 ±4.855.7 a 84.0±3.5a 56.3 16.556.3 a ±3.257.5 a 47.912.8 ab Mean wood wood Mean consumption consumption rate 1676.71 ef 173.2 1920.01 f 192.3 1500.0 + de+ 52.9 1500.0 5 3 .9 1 a 1.9 85.514.1 a 310.0 ±26.5310.0 a Total wood Total wood consumption 960.0 ± 52.9 c 960.0 ± 52.9 Means separated by different letters indicate significant differences (p<0.05) using Tukey-Kramer HSD HSD Tukey-Kramer (p<0.05) differences using significant indicate different by letters separated Means formosanus. 100150 626.7 b ± 72.3 500 350 1692.5153.0ef 50 300 1602.0193.1 ef 400 250 200 1226.01 d 144.7 ±6.5 55.1 a SEM), mean percent survival (% ± SEM), and mean soldier proportion (% ± SEM) for nine treatments of termite densities densities termite of treatments nine ± (% SEM) proportion for soldier mean (% ± and SEM), survival percent mean SEM), in C. Termite density Table 4.1. Total wood consumption (mg wood ± SEM), mean wood consumption rate (mg wood / g termites per day ± perday ± / termites (mg g wood rate consumption wood mean ± (mg consumption SEM), wood wood 4.1. Total Table procedure.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 400 500 300 350 250 Termite density Termite 200 150 100 . R2 = 0.99, p<0.0001 y = -57.1290 + 7.9674x - 0.0083x2 50 Figure 4.1. Relationship of total wood consumption amount (y: mg wood) to termite density (x) in C. (x) in C. density termite wood) to mg (y: amount consumption total wood of4.1. Relationship Figure formosanus 1000 1000 2500 2000

o a E 3 a 8 0 00 % E § 1500 1 •a {2 {2 500 ® H w •a

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Wood consumption rate (mg wood / g termites per day) 40 60 20 30 70 50 10 0 (x) in (x) Figure 4.2. Relationship of FigureRelationship4.2. of mean woodconsumptionrate (y:mg wood g / termites per day) to termite density 50 C. formosanus. 100 150 200 Termite density 250 300 y = 57.6380 + 0.0014x -0.0001x2 +0.0014x y=57.6380 R2 = 0.94, p<0.0001 =R20.94, 350 400 500 500 ------400 R2 = 0.84, 0.84, p<0.0001 = R2 y = 80.3820 80.3820 0.0349x = y + -0.0002x2 C. formosanus. C. 300 350 250 Termite density Termite 200 150 100 50 Figure 4.3. Relationship of percent survival of termites (y) to termite density in in density to termite (y) termites of ofpercent survival 4.3. Relationship Figure 100 c a> B t> a w ft.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 400 500 350 of the termination (x)the at 300 C. formosanus C. 250 Termite density Termite 200 150 100 R2 = 0.67, 0.67, = R2 p<0.0067 y~=T5;6704 +0.0208x y~=T5;6704 50 5 0 10 15 35 30 25 20 Figure 4.4. Relationship of soldier proportion (y) to termite density in in density to termite (y) proportion of soldier 4.4. Relationship Figure experiment. c o a e a k. o o 2 C/5 • f i Ov v£>

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. rapidly. Esenther (1985) suggested that the trophallactic efficiency among individuals

may decrease as population density in R.jlavipes increases. Trophallaxis is one of the

most important ways for termites to transfer food and pheromones among individuals

(Wilson 1971). In Formosan subterranean termites, the trophallactic efficiency may be

reduced when termite density exceeds 300-350 at the present experimental conditions.

Food consumption and termite survival are important parameters in laboratory

studies to evaluate the resistance of materials to termite attack (Lenz 1994). Termite

density in relation to food consumption and survival is an important factor for

evaluating results from laboratory bioassays. If the bioassay procedure is deigned to

compare food consumption rate and termite survival, termites must be allowed to have

a suitable population density. In the field, Grace et al. (1995) reported that larger

individual termite worker body mass is associated with the declined population density

and less vigorous termites in Formosan subterranean termites.

References

Becker, G. 1969. Rearing of termites and testing methods used in the laboratory. In: Biology of Termites. Vol. I. pp. 351-385. Krishna, K. & F. M. Weesner (eds.). Academic Press, New York.

Delaplane, K. S. and J. P. La Fage. 1987. Variance in feeding on equivalent wood blocks by the Formosan subterranean termite in laboratory choice tests. Sociobiology. 13:227-233.

Delaplane, K. S. and J. P. La Fage. 1990. Wood excavations o f three species of subterranean termites. Entomol. Exp. Appl. 54:81-87.

Esenther, G. R. 1985. The density factor in the termite bioassays. The International Research Group on Wood Preservation Working Group. Document No: IRG / W P/ 1252:1-5.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Gay, F. J., T. Greaves, F. G. Holdaway and A. H. Wetherly. 1955. Standard laboratory colonies of termites for evaluating the resistance of timber, timber preservatives, and other materials to termite attack. Aust. Commonw. Sci. Ind. Res. Org. Bull. p. 277.

Haverty, M. I. and W. J. Nutting. 1974. Natural wood-consumption rates and survival of a dry-wood and a subterranean termite at constant temperatures. Ann. Entomol. Soc. Am. 67:153-157.

Howick, C. D. 1975. Influence o f specimen size, test period and matrix on the amounts of wood eaten by similar groups of laboratory termites. Proc. A. Conv. Br. Wood Preserv. Ass. 51-63.

Howick, C. D. 1978. Influences of crowding during transportation on survival and laboratory feeding of termites (Isoptera). J. Inst. Wood Sci. 8:28-31.

Grace, J. K., R. T. Yamamoto and M. Tamashiro. 1995. Relationship of individual worker mass and population decline in a Formosan subterranean termite colony (Isoptera: Rhinotermitidae). Environ. Entomol. 24:1258-1261.

La Fage, J. P., N. -Y. Su, M. J. Jones and G. R. Esenther. 1983. A rapid method for collecting large number of subterranean termites from wood. Sociobiology. 7: 305-309.

Lenz, M. and E. R. Williams. 1980. Influence o f container, matrix volume and Group size on survival and feeding activity in species of Coptotermes and Nasutitermes (Isoptera: Rhinotermitidae, Termitidae). Mater. & Org. 15:25-46.

SAS Institute. 1989. SAS user’s guide: statistics. SAS Institute Inc., Cary, NC.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Su, N. -Y. and J. P. La Fage. 1984. Differences in survival and feeding activity among colonies of the Formosan subterranean termite (Isoptera: Rhinotermitidae). Z. Ang. Ent. 97:134-138.

Su, N. -Y. and J. P. La Fage. 1987. Effects of soldier proportion on the wood consumption rate of the Formosan subterranean termite (Isoptera: Rhinotermitidae). Sociobiology. 13:145-151.

Traniello, J. F. A. 1983. Social organization and foraging success in Lasius neoniger (Hymenoptera: Formicidae): behavioral and ecological aspects of recruitment communication. Oecologia. 59:94-100.

Traniello, J. F. A. 1989. Foraging strategies of ants. Ann. Rev. Entomol. 34:191-210.

Waller, D. A. and J. P. La Fage. 1987. Food quality and foraging response by the subterranean termite Coptotermes formosanus (Isoptera: Rhinotermitdae). Bull. Ent. Res. 77:417-424.

Wheeler, D. E. 1994. Nourishment in ants: patterns in individuals and societies. In: Nourishment and Evolution of Insects, pp. 245-271. Hunt, J. H. & C. A. Nalepa (eds.). Westview Press Inc., Boulder, Colorado.

Wilson, E. O. 1971. The Insect Societies. Belknap Press / Harvard University Press, Cambridge, Massachusetts.

Wilson, E. O. 1975. Sociobiology: the new synthesis. Belknap Press / Harvard University Press, Cambridge, Massachusetts.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER VI

EFFECTS OF MOISTURE AND TWO NITROGEN SOURCES ON NEST SITE CHOICE BY ALATES AND DEALATES OF COPTOTERMES FORMOSANUS SHIRAKI (ISOPTERA: RHINOTERMITIDAE) IN THE LABORATORY*

* Reprinted by permission of SOCIOBIOLOGY.

100

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Introduction

The swarm of subterranean termite alates is an important mode of forming new

colonies; colonies also are started by secondary reproductives (wing-padded neotenics)

(reviewed by Thome 1985, Shellman-Reeve 1997). Previous studies indicate that

temperature, humidity, rainfall, light intensity, wind velocity, and atmospheric pressure

affects the flight behavior of a Coptotermes formosanus Shiraki colony (Lai 1977, Lin

1987), although the relationship between climatological factors and flight phenology is

not obvious (Higa & Tamashiro 1983, Henderson & Delaplane 1994). However, it has

not been determined if specific environmental factors affect the nest site preference by

founding pairs of the C. formosanus.

Termite colonies are often patchily distributed in a forest ecosystem due to the

availability of preferred foods or other environmental factors (Waller 1991). Moisture is

possibly one of the more important environmental factors characterizing termite

distribution. According to Huang and Zhang (1980), low reproduction and egg-hatching

rate by new founding pairs of C. formosanus corresponded with a reduction of moisture

on a diet in the laboratory. Delaplane and La Fage (1989) reported that the wood

feeding rate and number of workers and soldiers of C. formosanus were the highest in

wood with high moisture in a choice test. Individuals of C. formosanus have no

mechanism to uptake water vapor from the atmosphere even with humidity close to the

saturation point (Rudolph et al. 1990), but dehydrated termites can restore water content

by drinking available water (Collins 1969). How moisture affects the nest site choice by

alates and dealates of C. formosanus is not known.

101

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Nitrogen availability has also been recognized as an important nutritional constraint

of wood feeding termites (La Fage & Nutting 1978, Waller & La Fage 1987, Shellman-

Reeve 1990, Nalepa 1994). Mauldin and Smythe (1973) reported four routes by which

termites could meet their nitrogen requirement, i.e., the fixation of atmospheric

nitrogen, from dietary protein, the digestion of symbiotic organism, and utilization of

‘microorganisms’ waste products. The dietary source is probably the most important

(La Fage & Nutting 1978). Chen and Henderson (1996) reported that four nitrogenous

compounds could increase feeding by workers of C. formosanus in the laboratory.

Likewise, Spears and Ueckert (1976) observed that food consumption by the desert

termite, Gnathamitermes tubiformans (Buckley), was positively correlated with the

increase of amino acid nitrogen levels on a diet. Amino acids may increase the fitness of

the colony by increasing colony nutrition. In fact, Shellman-Reeve (1990) found that

fecundity by nest-founding pairs of Zootermopsis nevadensis Hagen increased as the

concentration of dietary uric acid increased. Furthermore, new nest-founding adults of

Z. nevadensis showed a strong preference for the cambium layer of logs which is high

in nitrogen (Shellman-Reeve 1994). However, the question arises whether nest-

founding pairs of C. formosanus prefer sites with high nitrogen availability. We present

results of a choice test with C. formosanus in a light trap apparatus in which diets with

moisture and two different chemical additives were provided.

Materials and Methods

Termites. One colony of C. formosanus was field collected from an infested tree

in November 1997, from Algiers, Louisiana. The infested-tree section was cut into

transportable pieces, brought back to the laboratory, and held in plastic containers

102

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. (60cm diam., 75cm high) at room temperature (23-28 °C). The swarming of this

laboratory colony started in mid-April and ended in early-June.

The alate entrapment apparatus. The entrapment apparatus consisted of a light-

trap (BioQuip Products, Gardena, CA) equipped with a 22-watt circle fluorescent light

that turned on at 17:00 h and off at 8: 00 h the next day. Each of five light traps

contained six Petri dishes (85mm diam., 40mm high, Coming Co, Snap-Seal^M) §jx

small holes (6mm diam.) served as entryways for alates along the bottom of each Petri

dish.

Treatment design. The multiple-choice test was conducted using a randomized

block design with a two x three factorial structure. Petri dishes were randomly assigned

to each entrapment apparatus. Six pieces of corrugated-cardboard circles (65mm diam.)

were layered into each Petri dish as a food source. Corrugated-cardboard circles were

oven-dried for two hours at 80°C before use. Before placement in a Petri dish, dried

cardboard circles were treated with 13ml deionized distilled water with or without the

chemical additives of L-glutamic acid or urea (purity 99+ % by TLC, Sigma Chemical

Company, St. Louis, Missouri) having a final concentration of0.15 % chemical additive

(w/w). Five entrapment apparatuses were set up for each observation (N=4

observations). Nitrogen concentrations tested were based on the normal range of

nitrogen found in wood (0.03 % to 0.18 % w/w; La Fage & Nutting 1978, Hungate

1941). The amount of deionized distilled water added was 40 % of the weight of the dry

corrugated-cardboard. This moisture level was based on survivorship studies of adults

of C. formosanus (Huang & Zhang 1980). Petri dishes were divided into two treatment

groups: treatment group (1) consisted of only deionized distilled water treated

103

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. cardboard circles, with or without urea solution or L-glutamic acid solution and

designated as "moist diets". Treatment group (2), cardboard circles, with or without urea

solution or L-glutamic acid solution, were oven-dried for two hours at 80 °C, then left

in the laboratory environment for five hours. The final content of water was 6 % and

designated as "dry diets".

All light traps were monitored at the same time and surrounded one termite-holding

container at a distance of 150cm. For each observation period of 48 h, the number of

paired dealates and alates were counted in the Petri dishes. The test was conducted in

mid-April through mid-May.

Statistical analysis. The effects of moisture and chemical additives were tested on

nest site preference by ANOVA, followed by Tukey’s mean comparisons test. The

moist or dry effects and chemical additive effects were considered fixed effects, while

observations that were considered blocks were random effects. Mixed models were used

in the ANOVA analysis (SAS system for mixed models, SAS Institute, 1997). Number

of adults in each Petri dish were shifted into percentages of all adults entering one

entrapment apparatus to validate the ANOVA analysis during each observation date. If

no adults entered one entrapment apparatus, this entrapment apparatus was dropped

from the ANOVA.

Results

Nest-founding adults (N=368 pairs) showed a significant preference for moist diets

compared to the dry diets (F=81.75; df=l, 113; p=0.0001). This was also true for total

adults (dealates + alates, N=1535) (F=81.94; df=l, 113; p=0.0001) (Table 5.1, Figure

5.1). There were no significant differences among three treatments (the additive of urea,

104

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. L-glutamic acid, or control) in the group of dry diets both for new paired dealates

(F=0.64; df=2,56; p=0.5319) and total adults (F=0.84; df=2, 56; p=0.4392). In contrast,

the effect was significant for three treatments in the group of moist diets for both new

paired dealates (F=3.21; df=2, 56; p=0.0478, Figure 5.1) and total adults (F=4.19; df=2,

56; p=0.0201, Figure 5.1). O f the moist diets tested, the additive urea did not

significantly increased nest site preference of alates and dealates compared to the

control. L-glutamic acid appears to have an inhibitory effect on nest site choice by

alates and dealates (Figure 5.1).

The mean percentages (± SEM) of adults in Petri dishes treated with urea were

36.09 ± 5.72 % (paired dealates) and 40.45 ± 5.79 % (total adults), while the mean

percentages o f adults treated with L-glutamic acid were 18.43 ± 4.13 % (paired

dealates) and 18.56 ±4.51 % (total adults). The mean percentages of termites entering

the nest site treated only with deionized distilled water were 31.7 ± 5.39 % (paired

dealates) and 37.12 ± 6.74 % (total adults).

Discussion

The results presented here demonstrate that nest-founding Formosan subterranean

termites preferentially seek nesting sites with high moisture availability. Only 4 % of

the adults were collected on dry diets, indicating that nest-site preference is conditional

with respect to moisture availability. Huang and Zhang (1980) reported that only 12 %

of young colonies lay eggs and that eggs cannot hatch when water content of a diet is

lower than 19.6%. This indicates that moisture conditions directly impact young colony

development. Tamashiro et al. (1987) considered aerial colonies to be (1) those initiated

by alates (2) those where subterranean colonies move up into trees and structure, or (3)

105

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 77 2 41 22 Urea diets 18 10 53 16 2 51 7 39 2 2 9 31 2 12 15 16 12 15 0 4 27 6 10 14 20 + + alates) 1 1 0 0 42 0 0 adults (dealates adults Urea OD L GA Total L-GA Drv diets Drv i Moisten 0 0 0 4 00 3 0 0 0 OD in each Petri dish collected in the choice test. the choice dish in collected each Petri in 38 2 2 6 Urea 2 72 0 0 0 2 22 4 0 0 0 0 2 2 0 4 0 L-GA Moisten diets Moisten C. formosanus C. 10 10 10 4 14 2 3 0 10 8 4 4 8 6 2 OD Paired dealates II 0 0 0 0 00 0 0 6 6 0 0 12 20 10 0 0 Drv diets Drv Observation 0 0 0 0 0 0 0 0 0 4 4 2 2 0 0 0 0 Observation I Observation 0 0 0 OD4 L-GA* Urea Table 5.1. of ofNumber adults Table 5.1. o\ o

(Table 5.1 continued) 107 Urea collected in Moist diets formosanus Treatment combination for testing nest site choice L-glutamlc Urea Control L-glutamic Dry diets Dry New paired dealates □Dealates + alates Figure 5.1. Mean percentage (± SEM) comparison ofadults ofC. Tukey’s mean comparisons test. the test. Bars marked the same letter arc not significantly different (p > O.OS) using Control o oo

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. remnants of a colony that have become detached and found suitable moisture sources

above ground. Our results show that moisture is an important factor that may limit

colony initiation by alates of C. formosanus. In Waikiki and Honolulu, Hawaii, aerial

infestations with no ground contact make up more than 50 % o f all nests (Tamashiro et

al. 1987). Su and Scheffrahn (1987) reported that approximately 25 % of all nest sites

by C. formosanus are aerial infestations in urban southeastern Florida (See also Su et al.

1989). However, since new nest-founding pairs prefer high moisture, aerial infestations

by alates are improbable where there is no moisture.

Formosan termites do not appear to select nest sites in response to different nitrogen

compounds. Urea additive in cardboard disks can significantly increase food

consumption by workers of C. formosanus (Henderson et al. 1994), as well as L-

glutamic acid (0.01M) (Chen & Henderson 1996). In the present study, although urea

did not significantly increase nest site choice compared to the control by alates and

dealates of C. formosanus, urea still may contribute to the nutrient requirements of C.

formosanus. It is possible that bacteria in the rumen synthesize necessary proteins of

termites from urea and other non-protein sources (La Fage & Nutting 1978). Curiously,

L-glutamic acid appears to have an inhibitory effect on nest site choice by alates and

dealates. One possible explanation is that in wet diets fungi may grow, especially if

enriched with amino acids, that cause a repellent effect to alates and dealates over time.

This would not have been the situation in the previous feeding tests by Chen and

Henderson (1996) since diets were dry. According to La Fage and Nutting (1978),

glutamic acid contributes the highest percentage of all amino acids found in the bodies

of dry-wood termite alates, Pterotermes occidentis (Walker) and Marginitermes

109

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. hubbardi (Banks). The amino acid composition in termite alates is similar to other

animals (La Fage & Nutting 1978). This may suggest that the extra amount of L-

glutamic acid provided in the study was not necessary to termite alates since, unlike uric

acid, they are not largely deposited in fat body (Potrikus & Breznak 1980). Shellman-

Reeve (1990) reported that founding pairs of Z. nevadensis have much high uric acid

reserve compared to the third to penultimate instars (which tend to be the nutrient-

gatherers). It is possible that different termite castes need to meet different nutritional

requirements due to the division of labor.

References

Chen, J. and G. Henderson. 1996. Determination of feeding preference o f Formosan subterranean termite (Coptotermes formosanus Shiraki) for some amino acid additives. J. Chem. Ecol. 22:2359-2367.

Collins, M. S. 1969. Water relations in termites. In :Biology of Termites. Vol. I. pp. 433-458. Krishna K. & F. M. Weesner (eds.). Academic Press, New York.

Delaplane, K. S. and J. P. La Fage. 1989. Preference for moist wood by the Formosan subterranean termite (Isoptera: Rhinotermitidae). J. Econ. Entomol. 82:95-100.

Henderson, G. and K. S. Delaplane. 1994. Formosan subterranean termite swarming behavior and alate ratio (Isoptera: Rhinotermitidae). Ins. Soc. 41:19-28.

Henderson, G., M. L. Kirby and J. Chen. 1994. Feeding stimulants to enhance bait acceptance by Formosan termites. The International Research Group on Wood Preservation. May 29 — June 3, Bali, Indonesia. Document No: IRG / WP / 94-10055.

Higa, S. Y. and M. Tamashiro. 1983. Swarming o f the Formosan subterranean termite in Hawaii (Isopera: Rhinotermitidae). Proc. Hawaiian Entomol. Soc. 24:233-238.

Huang, L. and H. Zhang. 1980. Effects of temperature and humidity on young colonies o f Coptotermes formosanus. Acta Entomol. Sinica. 23:32-35 (in Chinese with English abstract).

Hungate, R. E. 1941. Experiments on the nitrogen economy of termites. Ann. Entomol. Soc. Am. 34:457-489.

110

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. La Fage, J. P. and W. L. Nutting. 1978. Nutrient dynamics o f termites. In: Production Ecology o f Ants and Termites, pp. 165-232. Brian, M. V. (ed.). Cambridge University Press, Cambridge, England.

Lai, P. Y. 1977. Biology and ecology o f the Formosan subterranean termite, Coptotermes formosanus and its susceptibility to the entomogenous fungi, Beauveria bassiana and Metarrhizium anisopliae. PhD Dissertation, Department of Entomology, University of Hawaii, Honolulu, Hawaii. 140 pp.

Lin, S. -Q. 1987. Present status o f Coptotermes formosanus and its control in China. In: The Biology and Control of the Formosan Subterranean Termite, pp. 31-36. Tamashiro, M & N. -Y. Su (eds.). College Trop. Ag. Human Resources, University of Hawaii, Honolulu, Hawaii.

Mauldin, J. K. and R. V. Smythe. 1973. Protein-bound amino acid content of normally and abnormally faunated Formosan termites, Coptotermes formosanus. J. Insect Physiol. 19:1955-1960.

Nalepa, C. A. 1994. Nourishment and the origin of termite eusociality. In: Nourishment and Evolution of Insects, pp. 57-92. Hunt, J. H. & C. A. Nalepa (eds.). Westview Press Inc., Boulder, Colorado.

Potrikus, C. J. and J. A. Breznak. 1980. Uric acid in wood-eating termites. Insect Biochem. 10:19-27.

Rudolph, D., B. Glocke and S. Rathenow. 1990. On the role of different humidity parameters for the survival, distribution and ecology of various termite species. Sociobiology. 17:129-140.

SAS system for mixed model. 1997. SAS Institute Inc., Cary, NC.

Shellman-Reeve, J. S. 1990. Dynamics of biparental care in the dampwood termite, Zootermopsis nevadensis Hagen: response to nitrogen availability. Behav. Ecol. Sociobiol. 26:389-397.

Shellman-Reeve, J. S. 1994. Limiting nutrient availability in a dampwood termite: nest preference, competition, and cooperative nest defense. J. Anim. Ecol. 63:921-932.

Shellman-Reeve, J. S. 1997. The spectrum of eusociality in termites. In: Social Behavior in Insects and Arachnids, pp. 52-93. Choe, J. C. & B. J. Crespi (eds.). Cambridge University Press, Cambridge.

Spears, B. M. and D. N. Ueckert. 1976. Survival and food consumption by the desert termite Gnathamitermes tubiformans in relation to dietary nitrogen source and levels. Environ. Entomol. 5:1022-1025.

I l l

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Su, N. -Y. and R. H. Scheffrahn. 1987. Current status of the Formosan subterranean termite (Isoptera: Rhinotermitidae) in Florida. In: The Biology and Control of the Formosan Subterranean Termite, pp. 27-31. Tamashiro, M. & N. -Y. Su (eds.). College Trap. Ag. Human Resources, University of Hawaii, Honolulu, Hawaii.

Su, N. -Y., R. H. Scheffrahn and P. M. Ban. 1989. Method to monitor initiation of aerial infestations by alates of the Formosan subterranean termite (Isoptera: Rhinotermitidae) in high-rise buildings. J. Econ. Entomol. 82:1643-1645.

Tamashiro, M., J. R. Yates and R. H. Ebesu. 1987. The Formosan subterranean termite (Isoptera: Rhinotermitidae) in Hawaii: problem and control. In: The Biology and Control o f the Formosan Subterranean Termite, pp. 15-22. Tamashiro, M & N. -Y. Su (eds.). College Trop. Ag. Human Resources, University of Hawaii, Honolulu, Hawaii.

Thome, B. L. 1985. Termite polygyny: the ecological dynamics of queen mutualism. In: Experimental Behavioral Ecology and Sociobiology, pp. 325-341. Holldobler, B. & M. Lindauer (eds.). Sinauer Associates, Sunderland.

Waller, D. A. 1991. Feeding by Reticnlitermes spp. Sociobiology. 19:91-96.

Waller, D. A. and J. P. La Fage. 1987. Nutritional ecology of termites. In :Nutritional Ecology of Insects, Mites, and Spiders, pp. 487-532. Slansky, F. & J. G. Rodriguez (eds.). Wiley and Sons, New York.

112

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER VII

SUMMARY

113

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. The Formosan subterranean termite is the most destructive, difficult to control, and

economically important species of termites in the southern United States. The purpose

of this study was to provide information on the biology and ecology of the Formosan

subterranean termite so that the effect of sibship on survival and fitness parameters of

primary reproductives may be clearly understood and bioassay techniques and

evaluation on termite baits are more efficiently employed. One objective of this study

was to study the incipient colony development of Coptotermes formosanus Shiraki

since no information is available on the consequences of genetic relatedness of primary

reproductives that establish new colonies in the Formosan subterranean termite. Seven

stock colonies of C. formosanus were collected in 1996 through 1997 in New Orleans

and Lake Charles. A total of 338 incipient colonies of sibling pairs or nonsibling pairs

of C. formosanus were set up. The study indicated that the effect of sibship on mate

mortality and fitness was significant. Nonsibling pairs suffered significantly higher

mortality than sibling pairs. However, the decreased success of outbred mates was

offset by an increased fecundity of offspring among established colonies. Either sibling-

or nonsibling-founded colonies from Lake Charles had a significantly higher survival

rate than colonies from New Orleans. Colonies from Lake Charles produced a

significantly higher number of larvae than colonies from New Orleans. The mismatch

of habits by mates from different environments and disease risks may be associated

with higher mortality in outbreeding. However, the heterozygous offspring of outbred

pairs may increase the genetic variation, provide greater adaptation to environmental

fluctuation, and harbor greater intestinal protozoan populations.

114

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. A series of laboratory studies was conducted to evaluate the influence of several

ecological factors on wood consumption and termite survival. The first study was to

determine the interplay of temperature and soldier proportion on worker survival and

wood consumption in the Formosan subterranean termite. The results indicate that the

soldier production is directly influenced by temperature. When the initial soldier

proportion was zero, soldier formation was at its highest rate at 30°C. Termite survival

was significantly higher at 30 °C after 12 d of testing. On average, termites had a

significantly higher survival rate when the soldier proportion was less than 20%. There

was a significant interaction of temperature by soldier proportion after 36 d of testing.

At 48 d, termite survival was significantly higher at 30 °C. There was no significant

decrease in survival rate as the number of soldiers increased at 25 °C and 33 °C. At

60 d, survival at 20 °C and 25 °C declined significantly when soldier proportion

exceeded 20%. At 30 °C and 33 °C, termite survival did not decline significantly until

soldier proportions exceeded 40%. Consumption rate increased significantly with rising

temperature up to 30 °C. Consumption rate significantly increased as soldier proportion

increased. It appears that C. formosanus are able to support higher numbers of soldiers

with the increase of temperature. The significant interaction of temperature by soldier

proportion on worker survival indicates that ecological factors of temperature and the

soldier proportion interact and counterbalance each other as termite colonies attempt to

attain efficiency in foraging.

The second laboratory study was to evaluate the effect of temperature and soldier

proportion on wood consumption rate and termite survival in the Formosan

subterranean termite. The results indicated that Formosan subterranean termites

115

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. consumed significantly greater amount of wood as wood volume increased. However,

wood consumption rate and termite survival were not significantly higher in wood

blocks with larger surface, given a constant volume of wood blocks. Wood blocks with

larger wood volumes may provide advantages in constructing more galleries with a

minimum of energy expenditure. A study of termite density and wood consumption and

survival of C. formosanus indicated that mean wood consumption rate and termite

survival did not significantly increase or decrease as population density increased.

However, when termite cohorts become crowded, wood consumption rate and termite

survival decreased rapidly. Food consumption and termite survival are important

parameters in laboratory studies that evaluate the resistance of wood materials to termite

attack.

The last study focused on the evaluation of moisture and two nitrogen sources on

nest site choice by alates and dealates of C. formosanus. The results indicated that nest-

founded C. formosanus prefer sites with high moisture availability to sites lacking

moisture. The additive urea did not significantly increase nest site preference of alates

and dealates compared to the control. L-glutamic acid appeared to have an inhibitory

effect on nest site choice by alates and dealates. It is concluded that moisture is a

precondition for infestation initiated by potential queens and kings. Aerial infestations

by new nest-founded pairs are improbable where there is no moisture.

116

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. APPENDIX: LETTER OF PERMISSION

Louisian* State University Agricultural Center Louisians Agricultural Experim ent Station Department of Entomo!o9y 402 Lrf# Sciences SuA&ng Baton R ouge. LA 7C6C3-1710 (£04) 390*1634 F it (504) 336-1643

January’ 11, 2000

Dr. David H. Kistner Professor of the Department of Biological Sciences California State University Chico, CA 95929-0515

Dear Dr, David H. Kistner:

I published a research paper entitled “Effects of moisture and two nitrogen sources on nest site choice by alates and dealates of Coptoiermes Jorntosanus in the laboratory ”, in Sociobiologv Vol. 34, No. 3. 1999. [ ant writing to you to get your permission to reuse this paper in nty dissertation. Your assistance would be creatly appreciated.

Sincerely yours.

Huixin Fci

117

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. VITA

Huixin Fei was bom 23 August 1964, in Jiangyin, Jiangsu Province, the People’s

Republic of China. Fei lived in Jiangyin and Nanjing most of his life. He graduated

from Luqiao High School in July of 1982, then moved to Nanjing to pursue bachelor of

science degree and master of science degree both in Entomology at Nanjing

Agricultural University, Nanjing, China. In July of 1989, he was assigned a position as

a faculty member in the Department of Plant Protection, Nanjing Agricultural

University. He married Wenli Jing in Nanjing in December of 1990 and they have one

daughter, Xianhan (Mary) Fei, bom 27 February 1992. The thing he most misses about

China, besides his family in Jiangyin and former colleagues at Nanjing Agricultural

University, is the delicious Chinese food. Fei is presently a candidate for the degree of

Doctor of Philosophy in Entomology at Louisiana State University, which will be

awarded on 19 May 2000.

118

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. DOCTORAL EXAMINATION AND DISSERTATION REPORT

Candidate: Huixin Fei Entomology Major Field:

Title of Dissertation: Comparative Biology and Ecology o f the Formosan Subterranean Termite, Coptotermes formosanus Shiraki (Isoptera: Rhinotermitidae) in Louisiana

ifessor and

aduate School

EXAMINING COMMITTEE:

(U?

Date of nation:

March 13, 2000

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.