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1985 Some Factors Affecting Male Back Space Availability in the Water Bug Belostoma flumineum Say Amanda M. VanDenburgh Eastern Illinois University This research is a product of the graduate program in Zoology at Eastern Illinois University. Find out more about the program.
Recommended Citation VanDenburgh, Amanda M., "Some Factors Affecting Male Back Space Availability in the Water Bug Belostoma flumineum Say" (1985). Masters Theses. 2788. https://thekeep.eiu.edu/theses/2788
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m Some Factors Affecting Male Back Space Availability
In The Water Bug Belostoma flumineum Say (TITLE)
BY
Amanda-M. VanDenburgh
THESIS
SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS
FOR THE DEGREE OF
Master Of Science
IN THE GRADUATE SCHOOL, EASTERN ILLINOIS UNIVERSITY
CHARLESTON, ILLINOIS
YEAR
I HEREBY RECOMMEND THIS THESIS BE ACCEPTED AS FULFILLING
THIS PART OF THE GRADUATE DEGREE CITED ABOVE
DATE
COM'MITTEE MEMBER
COMMITTEE MEMBffi /
DEPARTMENT tHAIRPERSON ABSTRACT
Various factors affecting the availability of male back
space in the giant water bug, Belostoma flumineum Say, are
described herein and interpreted in a manner consistent with
natural selection theory. Newly emerged males are observed to breed and accept eggs sooner than newly emerged females
develop an egg clutch; furthermore, newly emerged males were
shown to contain motile sperm on th e day of adult emergence.
Newly emerged females did not contain any mature eggs until
approximately six days old. It was also found that newly
emerged females manufacture eggs at a linear rate of 4. 8
eggs per day. Egg length was found to increase significantly with age; egg width did not. Asy nchronous breeding (one female ovipositing on more than one mal e) appears li kely to
occur. This would skew the operational sex ratio towards females since fully encumbered males or males which have
brooded eggs for several days (and are not receptive to further oviposition) are no longer available for mating.
Females appear to oviposit a partial clutch on an available
male rather than delaying breeding and yolking up a larger clutch that may completely encumber one male. To obtain a full pad, partially encumbered males may solicit eggs from more th an one female for up to five day s after original
ii oviposition. Since egg brooding constitutes a shareable parental investment, females should not prefer unencumbered males over partially encumberd males. If asynch ronous breeding favors a female biased operational sex ratio (OSR) and sexual maturation time favors a male biased OSR, then it seems logical that th e OSR will vary significantly throughout the breeding season. My results suggest that male back space may be limiting for female reproduction during th e early part of the summer, in which th e first nymphs have not yet matured, but probably is not limiting after young of-th e-year start emerging into the population.
iii ACKNOWLEDGEMENTS
I thank my graduate committee members: Dr. Kipp Kruse,
Dr. Michael Goodrich, Dr. William James, and Dr. Richard
Andrews for their help and support in my course work and th esis.
Special th anks to Dr. Kipp Kruse, my graduate advisor, for his statistical advice, humor, patience, and understanding throughout my graduate studies.
I would also like to th ank Mr. Max Markwell, Dr. L. B.
Hunt and all other who gave permission for th e use of their ponds during my research.
iv TABLE OF CONTENTS
Page
Co ver Page l.
Abstract ii
Acknowledgem ents iv
Table of Contents v
Introduction 1
Meth ods 9
Results 12
' Discussio n 16
Literature Cited 21
Tables and Figures 29
v INTRODUCTION
Ch arles Darwin (1871) first used the term "sexual selectio n" to describe the advantage one sex (usually males) has over conspecifics of the same sex in obtaining mates. We now recognize that sexual select ion occurs due to the differential reproduction of individuals and their genes.
Sexual selectio n is not a separate entity from natural selection, but rather one arena in which natural selectio n takes place (Barash , 1982) .
Trivers's (1972) theory of parental investment suggests that sexual selectio n will act primarily on the sex making the least investment, members of which will compete among themselves fo r access to members of the sex making the greatest investment. Trivers (19 72) first defined parental investment as "any investment by the parent in an individual offspring that increases that offspring 's chance of surviving (and hence reproductive success) at th e cost of the parent's ability to invest in other offspring. "
Generally , the relative parental investment tends to be asymmetrical between the sexes due to the initially large gametic investment made by the female. Trivers (1972) further argues that the smaller gametic investment by the male results in stronger selection on males to desert their offspring than that on females.
1 This initial discrepancy between the sexes in parental commitment is often maintained or exaggerate d by subsequent parental care by the female. As a result, the availability of females is generall y limiting for male re production within a population (Knowlton, 1982). Sexual sele ctio n is normally thought of as having two components - intersexual selection (ep igamic selection - Huxley, 1938) which usual ly translate s as female prefere nce for certain male phenotypes; and intrase xual sele ction which involves some type of male male competition. The evolutio nary consequences of this phenomenon are profound, and current literature is rich with examples of male mate -acquisitio n adaptations.
Parental investment can be further subdivide d into two catagories: shareable pare ntal investment and no nshare able parental investment (Wittenberger, 1981). Shareable parental investment is any investment in an individual offspring that does not re duce that pare nts ability to invest simultaneously in other off spring but do es reduce the parent's future repro ductive potential (i. e. guarding eggs, incubating eggs, bro oding young, and vigilance for pre dators
- Perro ne , 19 75; Wittenberger, 19 79). Nonshare able parental investment is any investment that cannot be invested simultane ously in more than one offspring (i.e. energy and nutrie nts inve ste d in gametes or individual offspring, food, time spent obtaining food, and gro oming offspring -
Wittenberger, 1981).
2 The difference between shareable and nonsh areable parental investments contributed by th e males is important when evaluating female mating preferences. If male parental investments are sh areable, this cost is negligible. If the parental investments are nonshareable, females should be more likely to seek an unmated male. Thus female mating preferences may be stro ngly influenced by the type of parental investment provided by males (W ittenberger, 198 1) .
In some species, paternal care is substantial and maternal care slight or no nexistent (Ridley, 1978). Examples of paternal care are fairly abundant and are found in a variety of species such as polychaetes (Reish , 1957;
Schro eder and Hermans, 1975) , insects (Cull en, 1969; Smith,
1976b), fish (Breder and Rosen, 1966) , amphibians (Salth e and Mecham, 1974) , and birds (Martin, 1974) .
Natural selection theory predicts that when males make the larger parental investment (which is often in the form of paternal care) one should exp ect some type of sex-role reversal. Females sho uld be the active sex and court males, and males become the "coy'' sex (Williams, 1966, 1975;
Burley, 1977) . Though extremely rare, what ap pears to be complete sex role reversal has been do cumented in insects
(Cullen, 1969; Smith, 1979b; Gwy nne, 198 1; Kopelke, 198 1;
Venkatesan, 1983), pipefish (T akai and Mizokami, 1959) , seahorses (Strawn, 1958 ) and birds (Jenni, 1974; Graul et. al. , 1977; Oring et. al. , 1981). Role reversed species are
3 often use d as example s to demonstrate that much of sexual be h avior and morph ology is influence d by th e re lative parental investment that each sex contributes (Williams,
19 66, 1975; Tr ivers, 1972) .
Petrie (1983) states that there are two primary situations which could lead to female competition fo r mates:
(1) where there is a variance in male quality and where there are fewer high quality male s than fe male s; and (2) where there is a shortage of available male partners and where male s invest more in reproduction than just the pro vision of game te s.
Among so me spe cies, fertilization occurs by sperm pre cedence , in which th e first male to copulate be co me s the genetic donor . In oth er cases, fertilization involves "sperm displace ment" or "last male advantage " in which the last male to copulate is reproductively succe ssful (Barash ,
1982) .
Paternity assurance is a spe cial consideration for insects because of th e females ability to store sperm in a spermatheca (Parker, 1970) . Stored sperm presents a potential for being cuckolded, i. e. broo ding eggs fertilize d by anoth er male (Trivers, 1972) .
One of the best studied example s of paternal care involve s th e giant water bugs (Insecta: He miptera:
. Be lostomatidae: Be lostomatinae - Torre-Bueno, 1906; Vo elker,
19 68 ; Smith, 19 76a, 1976b; Ko pelke, 1980; Venkate san, 1983) .
4 Prior to 1899, it was thought that the females carried the eggs (Dufo ur, 1863; Dirnmock, 1886; Comstock and Comstock,
1899) . Slater (1899) was the first to credit the male for the egg carrying. Torre Bueno (1906) agreed with Slater in believing the male "chafed under the burden. " Both scientists observed the male supposedly "trying to rid himself of eggs by passing his third pair of legs over the dorsum. "
These observations, however, are not consistent with mo dern natural selection theory. Natural selectio n could not favor females to oviposit their eggs in an undesirable environment. Therefore, the back of the male must be the optimal oviposition substrate. The behavior observed by previous workers was not an attempt to rid th e male of eggs, but rather to insure that the eggs had a constant oxygen supply and to remove toxic embryonic metabolites (Smith ,
1976b) . Eggs naturally brooded by males have a 95-100% hatching success, whereas eggs deposited in sh allo w water were attacked by fungi, and eggs experimentally removed from males and placed in air became desicated.
Paternal care interferes with a male's potential for future matings since time spent caring for eggs is time lost for courting and mating other females (Smith, 1980b) .
Natural selectio n should operate in such a way that caring males sho uld require a high assurance of paternity for eggs in order to reap the benefits of their labor.
5 Natural selection theory predicts that a male should
care for eggs or young only when the confidence of paternity is high. Male water bugs force the female into copulating
several times before receiving any eggs. In order for a female to deposit all of her eggs on a male's back, she may be required to copulate more than one hundred times (Smith,
1980a).
Smith (1979b) states that female water bugs of the
Belostomatinae, unlike other female insects, must encounter and encumber a male in order to lay eggs. This in itself may cause an alteration in female courtship, but before complete sex role reversal can be expected it must be demonstrated that male back space is a limiting factor in female reproduction (Smith, 1979b) .
Emlen (1976) introduced the term "operational sex ratio" (OSR) as an index for characterizing the mating system of animals. It was defined as the "average ratio of sexually active males to fertilizable females at any given time. " If the OSR is strongly biased toward one sex, the competition for mates increases for that sex, and intense
sexual selection occurs (Emlen and Oring, 1977) . Because fertilized females are often no longer available to would-be
reproducing males in many species, the operational sex ratio
is often strongly male biased (Barash, 1982) .
The availability of male back space can limit female reproduction if: (1) the adult sex ratio is female-biased;
6 (2) the male brooding period (and/or post-brooding
refractory period, which would replenish energy stores) is
longer than the time required for females to synthesize a new clutch; (3) the sexual maturation time of newly emerged adult females is shorter than that of newly emerged males;
or (4) asynchronous breeding occurs (one female deposits eggs on more than one male) (Kruse, pers. comm. ).
Water bugs have been used as examples of role-reversed
species, but outside of Abedus (Smith, 19 76a, 1979b), little
has been done in the way of studying the limited male back
space situation.
The water bug, Belostoma flumineum Say is a voracious, predatory insect found in temporary and permanent ponds throughout the United States. It is the most common North
American member of the genus (Smith, 19 76b). The eggs are attached to the dorsum of the male in a mucilaginous cement
pad (Lauck and Menke, 1961) . Males brood the eggs until the
nymphs hatch (6-12 days - Torre-Bueno, 19 06). This species
is paurometabolous (Mccafferty, 1981), and after hatching,
they proceed through five nymphal instars before they become reproductive adults. The time from egg oviposition to adult ranges from 45 to 54 days (Torre-Bueno, 1906). Encumbered
males have been collected mid-May to late August (in New
Jersey) and the adult stage over-winters (Torre Bueno,
1906). Because of its prevalence in east-central Illinois
and because it is relatively easily maintained in captivity,
7 this species was chosen as a study vehicle to inve stigate the possibility of a limited male back space phenomena.
Factors that influence sexual se lectio n in B. f lumineum examined in this study ar e: (a) newly emerged adult fe male egg pro duction rates, (b) newly emerged adult male dorsum surface areas, (c) egg pad sizes of adult males, (d) sexual maturation time s for newly emerged adults, (e) sperm presence in newly emerged adult male s and (f) female inter clutch intervals. Re sults from these experime nts should give _ insight into the relatio nship be tween male back sp ace availability, female egg production, the OSR of B. flumineum, and eventually, to add to kno wledge of sexual selection in species with exclusive post-co pulato ry paternal care.
8 periodically (usually every 48 hours) beginning with the day of emergence (day 0) and ending with day 20 i. e. those preserved on day 20 were 20 days old. Females were weighed to the nearest 0. 0001 g both daily and irmnediately prior to preservation using an analytical balance.
The preserved females were dissected by cutting along the posterior margin of the pronotum and down the sides of the body. The dorsum was removed and the number of mature eggs (large, yellow eggs with one end of the egg having a reddish color at the presumed abscission line) was counted.
Ten randomly selected ova were measured for length and width using an oc�lar micrometer.
A preservation schedule was also prepared for the newly emerged males; three to five bugs were preserved per day starting at day 0 and continuing through day 16. Males were weighed daily including the day of preservation.
To calculate male back space area, an apparatus was built in which a 100 watt light bulb was illuminated upwards through a glass plate. The preserved males were placed on top of the glass and covered with an inverted plastic petri dish (the sides of the dish had been sanded down until it just covered the bug without crushing it) . A piece of tracing paper was placed on top of the dish and a sil houtte was drawn of the entire bug. The silhoutte was then placed under a grid transparancy (1 square = 2 nun) and the area of each male's back space was estimated by counting grids.
10 In order to test for sperm presence, lab reared males were decapitated with a razor blade. The dorsum was removed and the testes dissected out and placed in insect Ringer's solution. The testes were then placed on a clean slide and a cover slip was added. Using a light microscope under dark field the presence of sperm was verified.
To examine reproductive maturity, a newly emerged adult was placed with two "mature" bugs (30 days or older) of the opposite sex. Bugs used for this experiment were kept isolated from bugs used in the previous experiments. These were placed in standardized containers and left undisturbed for one month except for daily checking for oviposition.
The number of eggs in a male pad was calculated using fourteen "full" discarded egg pads preserved in alcohol.
Using a dissecting scope, the number of eggs for each pad was counted.
Finally, a series of females (both field captured and lab-reared) were supplied continually with unencumbered males (at least 30 days old) . As matings occurred, it was recorded how many eggs were laid, how often, how long a male retained his pad and whether or not he brooded the eggs successfully (to hatching).
11 RESULTS
Female Sexual Maturation
The relationship of female body weight (g) to age (days since adult emergence) is shown in figure 1. As expected, older females were significantly heavier than younger females. Similarly, older females tended to contain more mature eggs than younger females (fig. 2). The regression analysis suggested that as females mature, an average of 4. 8 eggs are added per day; which probably accounts for the weight increase displayed in fig. 1. Despite constant feeding rates and other environmental conditions, the number of eggs varied considerably within each age class.
Obviously, it takes a certain amount of time for a female to yolk up a clutch because no mature eggs were found in females less than four days old.
After the females had been dissected, ten ova were randomly selected per female and egg lengths and widths were calculated using a dissecting scope micrometer. From these a mean egg length and width was calculated for each female.
Although a considerable amount of variance exists, older females tend to have significantly longer eggs (fig. 3); howe ver, mean egg width was found to be uncorrelated with female age (fig. 4).
12 Male Back Space
A series of morphological mea!::>urments were made using a
dial caliper on lab-reared and field captured males (fig.
5). All males were measured within one month after
preservation. The il lumination technique provided an
effective way to demonstrate variations in male back space
surface area. As expected, males with longer body lengths
tended to have larger surface areas (fig. 6). Surface areas
ranged between 120 mm2 to 190 mm2, however, of the 50 males,
64% had surface areas between 150 mm 2 and 170 mm2 .
Newly emerged lab-reared males were used for
comparisons to weight, total length, body length, and
surface area. As expected, heavier males tended to have
larger total length (fig. 7) . Though not as strongly
correlated, male body length was also correlated to weight
(fig. 8). Males with longer body lengths tended to weigh
more than males with shorter body lengths.
Older males tended to have larger surface areas than recently emerged males (fig. 9). Males at age zero had the
most variant surface area. Areas for this age class were all
less than 155 mm 2. All other age classes (except one four
day old) had surface areas greater than 150 mm2 .
Number of � Per Pad
Of the fourteen "full" egg pads sampled, egg counts
ranged from 131 to 19 6 eggs/pad with a mean of 156 eggs and
13 a standard deviation of 20 eggs (fig. 10) .
Reproductive Maturity of Newly Emerged Adults
Of the nine newly emerged females, only five oviposited. And of the 16 males used, only 1 accepted eggs
(Table 1). Newly emerged females showed a mean age of ov i position of 1 0. 8 days ( f 7 . 5 days � � � 14. 1 days = 0. 9 5) .
None of the females oviposited sooner than eight days. The one male accepted eggs after only five days and brooded these eggs to hatching.
Sperm Presence in Newly Emerged Males
Of the six newly emerged (age 0 days) used, all had sperm present with four of the males having active sperm.
One five day old male was also subjected to this test. He too had active sperm present.
Asynchronous Breeding
Although the data are extremely limited, Table 2 shows how asynchronous breeding can limit male back space. For example, female #4 oviposited on four different males within a period of 17 days.
The number of eggs a male will brood to hatching is demonstrated in Table 3. It appears that males which are less than 50% full have a tendency to lose the pad before hatching occurs. It has been noted that when males are
14 disturbed they will kick off the pad. However, Smith (1976b} found that the use of structure in the holdin g container eliminates this problem. Therefore, the males in this experimen t did not lose their pads due to an artif act of experimentation.
15 DISCUSSION
Smith (1 979b) theorizes that male back space in water bugs may be a limiting factor for female reproduction, which could ultimately lead to sex role reversal. This study reports on factors that aff ect th e operational sex ratio
{OSR) and partially serves as a test of Smith 's hypothesis in the water bug �- flumineum.
One factor af f ecting waterbug OSR is the sexual maturation time of newly emerged adults. Since it appears that newly emerged males can accept eggs bef ore newly emerged females can yolk up a clutch, this would result in an operational sex ratio male skewed. This is an important observation in water bugs because the population from July to August consists of young of the year adults; the over wintering populatio n has totally disap peared by mid- to late
June {Kruse, pers. com.).
My data suggests that in the newly emerged female egg development is a continual process (i. e. egg number increases with age). Approximately five eggs per day are manuf actured following emergence, and generally no mature eggs are present in females less than six days old. These data suggest that females canno t breed until seven to ten days after emergence. These egg count data are congruent with my observations that newly emerged females require an
16 average of ten days to oviposit on males. Smith (1979b) states that egg production continues uninterrupted in Abedus herberti (when food is plentiful) until the female is filled to capacity . If no male is present, the female then discards the oldest eggs on vegetation or rocks. This presumably insures that relatively fresh eggs will be in constant sup ply . This egg discarding behavior of B. flumineum was observed many times in the laboratory.
Although the data are limited, the one newly emerged male bred at only five days old. I have additional observations suggesting that motile sperm are present the day of emergence. Whether this sp erm is viable or not is not known but Kruse (pers. com. ) has observed of a male breeding one day after emergence. This evidence of early breeding capabilities of males is only circumstantial, however, since the ovipositing females were non- virgins, thus sperm may have been stored in the spermath eca.
The rel atio nship between egg number and weight of females has been noted in several species of insects
(see review by Hinton, 1981). Heavier females co ntain more eggs and are thus more fecund. Gwynne's (198 1) study of
Mormon crick ets demo nstrated that th e mean weight of females rejected in matings was significantly less than successf ully mated females. Thus, according to Petrie (1983), in role reversed species, a high quality female would thus be those that produce th e most, and/or largest eggs.
17 Besides egg number, egg length also increases with female age. Smaller eggs contain less yolk, therefore, less food for young. This could mean a lower pro bability of success for hatching nymphs. This may result in wasted gamete production if the young die from malnutrition bef ore or shortly after hatching. It is interesting to note that egg width did not vary signif icantly with age, whereas length did and that egg width did not vary greatly within each female. Female oviduct size may be a constraint on egg width .
My data also suggest that females must ovipo sit a critical number of eggs in order for males to retain th e pad until the nymphs have hatched. It appears that when less than 50% of the male's back space is covered, the pad does not stay glued to his back. At this time it is not known if a male kicks of f a small pad or if such a pad is "unstable" and falls off, alth o ugh I suspect that it is the latter.
If females are to compete with each other to obtain high quality males, females should have some way to assess male quality (a high quality male being one that can contribute the most to a female's reproductio n - Petrie,
1983) . Older males tend to have larger backspaces than younger males. Theref ore, older males can bro od more eggs.
This could account for the wide range of eggs found on the fourteen "full" males. In order to obtain the most for his reproductive eff ort, a male should brood as many eggs as he
18 can successfully carry. Thus he should either mate with a single female that can fully encumber him, or several females with small egg clutches.
It appears that a female will oviposit on the first available male rather than waiting to yolk up a larger clutch that would fully encumber a male. Since these bro oding behaviors constitute a "shareable parental investment'' (up until the male's back is full) , females should not prefer unmated males over mated males. Smith
(1979b) found that serial polygamy (male with eggs fro m more that one female) routinely occurred in Abedus herberti with males bearing immature eggs. He reasoned that this is because a heavily gravid female should encumber any male regardless of the attributes he displays, rather than discarding or depositing the eggs on substrate. However, he did find that males only accepted eggs up to abo ut five days af ter original oviposition.
Another factor aff ecting male back space is breeding asynchro ny i.e. females mating with more than one male. My data are limited, but it does show that a single female can oviposit on more than one male and thus preempt these males within a short period. Even with a 1:1 adult sex ratio, asynchrony may skew the OSR to be biased towards females since bro oding males, with full or well developed egg pads are sexually unavailable for mating. Smith (1979b) states that this asynchrony and female competition, once
19 established, could continue throughout the summer month s even when food is abundant.
It is interesting to note that sexual maturation time favors a male biased OSR, but asynch ronous breeding favors a female biased sex ratio. These conflicting factors may cause the OSR to vary signif icantly throughout the summer. For example, Iwasa et. al. (1983) described a butterf ly population (Euph ydryas editha) in which the OSR fluctuated signif icantl y throughout the flying season. The OSR appeared to be dependent upon the mortality rates of preemerged and adult males, and insensitive to female emergence rates.
It appears that male back space may be limiting for at least that part of the year in which the first clutch of nymphs has not yet emerged to adulth ood. Therefore, during this time, over-wintering females are competing for back space of a limited number of over-wintering males. Further research needs to be done to determine factors that affect the OSR in B. flumineum throughout th e entire season.
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28 Fig. 1. The relationship of body weigh t (g) to age
(days) since adult emergence of female� flumineum
+ 2 (Y=.298 .0029(X); n=21; r =. 755; �<0.01). Note - the
regression was computed using the means {+l S. E. ) of daily
r weights (sample size of which are in pa enthesis ) .
29 .38- . I .:. - . 0) � .36 I ·- 11 -- 10 :I: 16 10 -- <-' - - UJ .34 !! T � UJ J3 · :2 .32 36 � J UJ "'- .30 --1--r-- 38 .28 i
0 .2 4 6 8 lO 12 14 16 18 20·
AGE (days) Fig. 2. The relationship of egg number to age (days) since adult emergence of fem ale B. flum ineum
(Y=2. 72 + 4. 77 (X) ; n=41; r2=.523; �<0.01).
30 00 .-4
"' � Q G> (%) .-4
- r/) :>. 0 0 � ca 1""14 "tS - L1J 0 N (!) ' QQ Q (!) 1""14 N 0 O· 0 00 � N SD93 .:10 H39WON Fig. 3. The relationship of mean egg length (±1 S.E.) (n=lO eggs/female) to age (days) since adult emergence of 2 female B. flumineum (Y=l. 74 + .0097 (X) ; n=29; r =. 320; P<0. 01) . 31 -0- 0 N \0 -0 ..c - � � � ..c 40 � - N UJ --0- � C) --0---0- --0-- " c( UJ 0 .J � ..c < --0-- � UJ u.. -<>- 1 :Q_(S (;/'\ 0. . N {UrtU) 5993 .:10 H.tDN31 N\13W Fig. 4. The relationship of mean egg width {�l S.E.) {n=lO eggs/female) to age {days) since adult emergence of femal e B. flumineurn (n=29; r2=.086; no correlation) . 32 N N -<> 0 0 .<). N -0- -0- GO ... -0.. <> '° � .... - � Cit -0-� .... � fO -.,, -<> <> -0- N Ll.J -<> -0- .... (!) � < UJ 0 ..J .... < � LIJ <> u.. -i>'°" -0- -0- N• 0 co '° � ,N 0 • °' °' °' °' °' ...... • • • • • (WW) SDD3 :JO H.LOIM NV3W Fig. 5. Body measurements used for estimating mal e back space dimensions. 33 Fig. 6. The relationsh ip of surface area (mm) to body length (mm) using lab-reared and field captured adult male male B. flumineum (n=SO; r2=.386; P<0.01) 34 190 0 0 0 0 180 0 0 0 ,,,,,... 0 0 N 170 0 0 E 0 0 0 e 0 0 ._... 0 0 < 0 � 160 0 CZ: OS° ., 0 130 0 0 0 120 ...... ------17 18 19 20 21 22 23 I MALE BODY LENGTH (mm) Fig. 7. The relatio nship of body weight (g) to total length (nun) using la b-reared adult male B. flumineum (n=l8; r2=. 501; P<0.01). 35 N 0 • N ff') ff') ff') • N N • . • • (6) J.H913M 31VW Fig. 8. The relationship of body weight (g) to bo dy length (mm) using lab-reared adult male B. flumineum (n=l8; r2=.399; P<0.0 1). 36 N N 0 0 0 0 0 .... N 0 0 0 - 0 0 E 0 -E (;) 0 0 ::i: f- O· N z LLJ 0 0 ..J > 0 0 :0 0 °' ..... 0 (6) .LH!>l3M 31\t'W Fig. 9. The relationship of surface are a (mm) to age (days) since adult emergence of male B. flumineum (Y=l43.8 + l. 57( X) ; n=20; r2=.432; f<0.01) . 37 \Q - 0 0 0 0 0 0 0 0 0 0 0 QO ...... lf) N - - - - - ( 1: tu w ) V ::1 H V 3 :J V .:I H n S Fig. 10. Fully encumbe re d male 's egg count (n=l4 ; x=l56 eggs; s=20 eggs; range=l31-196 eggs) . 38 n=14 :i:=156 eggs s=20 eggs range=131 - 196 Table 1. Age of newly emerged adults at time of first mating. Male brooded Age when first # eggs eggs to Sex oviposited (days) oviposited hatching? females 8 14 no 9 34 yes 11 91 yes 12 no ] 4 male 50% full no x=l 0.-8 days s=2.6 days male 5 male 50� full yes ..,., Q;;/ Table 2. Time elapsed fro m oviposition to subsequent oviposit ion and nu mbe r of eggs oviposited (females 1, 2, 3, and 4 were field captured adults; fe mal es 5, 6, and 7 were reared adults). fe male # days since # eggs number last oviposition oviposit ed 1 male 75% full 10 male 75% full 2 ma le 50%+ full 7 41 " 3 male 2 :Jr- ·.:. full 4 male 75% full 4 27 9 56 - 7 i - 1 .:i. I t:. ..) 52 ... ;) 76 6 14 9 39 7 7 9 9 r , 4- \.: Table 3. The relationship of egg pad size to brooding success. % Encumbered # days Brooding to Age of or # of eggs pad was on hatchinq? female 100% 10 yes ? 90% 9 yes ? 90% 8 yes ? 75% 10 yes ? 50+% 4 no ? 50% 1 no ? 25% 5 no ? 24 Sf. (58 eggs) 10 no 12 days 22% (56 eggs) 3 no 25 days 20% (52 eggs) 9 no 11 days 18% ( 41 eggs) 5 no ? 16% ( 3 9 eggs) 5 no 8 days 9% ( l 8 eggs) 5 no 12 days 7 So ( l 4 eggs) 3 no 8 days 5% (9 eggs) l no 21 days 3% ( 7 eggs) 1 no 12 days ? = field captured female 41