This dissertation has been microfilmed exactly as received 66-13,704
HARAMOTO" Frank Hiroshi, 1924- BIOLOGY AND CONTROL OF BREVIPALPUS 'PHGENICrs (GEIJSKES) (ACARINA: TENUIPALPIDAE).
University of Hawaii, Ph.D., 1966 Zoology
University Microfilms, Inc., Ann Arbor, Michigan .BIOLOGY AND CONTROL
OF
BREVIPALPUS PHOENICIS (GEIJSKES)
(ACARINA: TENUIPALPIDAE)
A THESIS SUBMITTED TO THE GRADUATE SCHOOL OF THE
UNIVERSITl OF HAWAII IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE OF
DOC TOR OF PHILOSOPHY
IN ENTOMOLOGY
JANUARY 1966
By
Frank Hiroshi Hararnoto
Thesis Comrn.ittee:
D. Elmo Hardy, Chairm.an Henry A. Bess Marnoru Ishii Wallace C. Mitchell Toshiyuki Nishida iii
TABLE OF CONTENTS
LIST OF TABLE; ••• 0 • · ...... iv liST OF ILLUSTRATIONS •••a••••••••• v
INTRODUCTION •••••••• · ...... 1 TAXONOMIC STATUS ••••• · ...... 3 DISTRIBUTION •••••••• ·...... 5 HOST PLANTS •••••• ·...... 10 METHODS AND MATERIAJ..S • ...... 14
DE;CRIPTION OF liFE STAGE; • • • • • •• •••• • 24
LIFE HISTORY••••••••• ·...... 42
BIOLOGICAL OBSERVATIONS • • • • • • • • • • • • • 57 POPULATION STUDIE; · ...... 67
NATURAL CONTROL FACTORS • • 0 • • • • • •••• 7I
CHEMICAL CONTROL...... 78 DISCUSSION ••• ...... 91
SUMMARY •• 0 • • •• 97
REFERENCES CITED •• •• 101 iv
List of Tables
Table
I. Geographical distribution of Btevipalpus phoPcnicis (Geij skes) •• ••••••••••••• 6
il. Monthly maxiInum-minimum temperatures for Honolulu and Kaneohe, Oahu, and for Kahului, Maui, during 1962 and 1963 •••••••••••••• 9
ID. List of host plants of Brevipalpus phoenicis (Geij skes) in Hawaii ••••••••••••••• •• 11
IV. Average measurements of ~he life stages of
Brevipalpus phoenicis (Geijskes). • I> ••••••• 27
V. Effect of temperature and humidity on the life
stages of Brevipalpus phoenicis (Geijskes) •• 0 •• 44
VI. Performance of different pesticides against the adults of Brevipalpus phoenicis (Geij skes) ••••• 86
Vil. Number of eggs of Br,evipalI?us phoenicis (Geij skes) counted on treated surface one week after application of the different pesticides ••••• 88
VID. Ovicidal effect of different pesticides on the eggs of Brevipalpus phoenicis (Geijskes) •••••• 90 v
List of Illustrations
Figure
1. Distribution map of Brevipalpus phoenicis ••••• 7
2. Rearing unit used in the constant temperature and humidity experiments • ••• .. ••••• • • 18
Rearing unit used in the chemical control studies of BrevipalP\;1s phoenicis •••••••••• • • 21
Outline drawing of Brevipalpus phoenicis female ehowing location and nomenclature of the
setae and plates ••••••••••.••••• 0 25
5. Egg of Brevipalpus phoenicis. •••••••••• 29
6. Larva of Brevipalpus phoenicis. ••••••••• 31
7. Protonymph of Brevipalpus phoenicis ••••••• 33
8. Deutonymph of Brevipalpus phoenicis ••••••• 35
9. Female of Brevipalpus phoenicis •• 0 • • • • • • 37
10. Variation in color patterns of females of
Brevipalpus phoenicis •••••• oi ••• 0 • • • 38
11. Male of Brevipalpus phoenicis ... .0. .... 41
12. Mean number of eggs laid per week by 25
Brevipalpus phElenicis female s • • • • • 0 0 0 • • 53
13. Longevity of the adults of Brevipalpus phoenicis at the different temperatures in combination with 65 to 70 per cent relative humidity •••• •• 56
14. Feeding injury caused by Brevipalpus rhoenicis on papaya fruit ••••• 0 0 • • • • • • • • •• 59 vi
IS. Feeding injury caused by Brevipalpus phoenicis
on papaya fruit ••••••••••••••• o 0 61
16. Feeding damage caused by Brevipalpus phoenicis
on passion fruit. ••••• 0 • • • • • • • • 62
17. Egg and adult densities and fluctuations of
Brevipalpus phoenicis populations. • 0 0 0 68
18. Injury caused by Chlorobenzilate • o 0 0 ... . . 82
19. Injury caused by Pentac • 0 • • • 83
20. Injury caused by ovex .0 . . . . ••• I! 84 rnTRODUCTION
The red and black flat mite, Brevipalpus phoenicis (Geijskes), has been reported from many countries since its discovery in Holland
in 1939 (Geij skes, 1939). This mite is not endemic to the type locality,
but is believed to have a tropical origin. However, because of its
extensive geographical distribution and host range, the native home of
this mite cannot be established.
Baker in 1949 reported that several species of Brevipalpus have
been found to be pests of cultivated plants, and although not as impor
tant as the spider mites they are serious enough at times to warrant
investigations of their biology and control. Since then, Manglitz and
Cory (l953) and Morishita (1954) have studied in detail the biology and
control of B. californicus (Banks) and of Jh obovatus Donnadieu,
respectively. These two species along with!h phoenicis and!h lilium.
Baker make up the known fauna of false spider mites of the genus
Brevipalpus in Hawaii. Of these, !h phoenicis is of most concern here
in Hawaii for besides damaging many ornamental plants, it attacks
two crops of significant economic importance: papaya and passion fruit.
~ phoenicis may have been in Hawaii previous to its description
date for in 1936 Marlowe (1937) reported a mite injury on papaya fruits
with symptoms similar to those now known to be caused by this species.
Despite its early presence in Hawaii, very little work has been done in
the past on this important mite by other worker So Therefore, a detailed 2. biological study ofl!: phoenicis has been made and the findings are presented in this thesis so that they may serve as a basis for further studies of this as well as other species of phytophagous mites. 3.
TAXONOMIC STATUS
B. phoenicisbelongs to the order Prostigmata, sl!perfa:mily
Tetranychoidea, and fa:mily Tenuipalpidae. Geij skes in his descrip tion of phoenicis in 1939 placed it in the genus Tenuipalpus. At that time, Brevipalpus was considered as a synonym of Tenuipalpus; how ever, Baker in 1945 established the validity of the for:mer and reinstated it as a generic name.
Unaware of the extent of possible variations in certain charac ters of B. phoenicis, Baker P949) na:med~ yothersi, ~ mcbridei, and B. papayensis as separate entities based on the differences noted in the size of the dorso-lateral setae of the nymphs of yothersi and
:mcbridei, and on the presence of a prominent edentation on the second palpal segm.ent, as well as on the less distinctive areolate pattern on the dorsum of papayensis adults. In later studies, these characters
were found to be :merely intraspecific variations, and thus, the three
names were declared as synonyms of B. phoenicis (Pritchard and
Baker, 1951).
In Hawaii, prior to 1951, B. phoenicis was referred to as~ bio
culatus McGregor (Holdaway, 1941), and as B. papayensis (Baker,
1949). The former is a misidentification and a synonym of B. obovatus,
a species very similar in gross morphology to B. phoenici~, and the
latter is a synonym. of B. phoenicis. The na:me, B. papayensis, was
proposed in 1949 by Baker for the :mites on papaya collected in 1941 by 4.
w. C. Look from Kailua, Oahu, Hawaii.
At present, there is no appt"oved common name for B.
phoenicis. The common name, the red and black flat mite, was first
used by Muma (1961) and is adopted to referring to~ phoenicis in
- this paper. DISTRIBUTION
!h E!!.oenicis is widely distributed in both continental and insular areas, primarily throughout the tropics of the world. Of the 28 distributional records, 18 have been reported from somewhere within the boundaries of the Tropic of Cancer to the north and the Tropic of
Capricorn to the s·outh (Fig. 1 and Table I). The northernmost area from where B~ phoenicia has been reported is Holland (Geijskes, 1939) and the southernmost is Argentina (Baker, 1949). The few reports of recoveries of this mite from other than the tropics probably represent temporary establishments as a result of dispersal from the generally favorable range into pockets of favorable environment. The outbreaks
of ~ phoenicis reported in glasshouses in Europe are exam.ples of such
dispersal and fortuitous establisbm.ents. Since its initial description in
Holland in 1939, B. phoenicis was not observed again in Europe until
1951 when it was found infesting Phoenix canariensis Hort. in glass
houses in Vienna, Austria (Dosse, 1957). The only areas outside the
tropics where B. phoenicis is firmly established are in Florida (Muma,
1958) and in the Mediterranean region (Baker, 1949; Attiah, 1956; and
Di Martino~ 1960) where the climate is mild and similar to that of the
tropics.
In Hawaii, B. phoenicis has been recovered from the islands of
Maui, Hawaii, Oahu, and Kauai. It is generally well distributed along
the coastal plains and foothills up to about 1, 000 feet in elevation. 6.
TABLE I. GEOGRAPHICAL DISTRIBUTION OF BREVIPALPUS PHOENICIS (GEIJSKES)
Continent Area * Reference
Africa Belgian Congo (1) Baker and Pritchard, 1960 Egypt (Z) Attiah, 1956 Kenya (3) Pritchard and Baker, 1958 Mauritius (4) Mou1ia, 1958 Tanganyika (5 ) Pritchard and Baker, 1958
Asia Aden Protectorate (6) Knorr, et al., 1961 Australia (7) Commonwealth Institute of Entomologyp 1959 Ceylon (8) Baptist and Ranaweere, 1955 Formosa (9) Pritchard and Baker, 1958 India (10) Pritchard and Baker, 1958 Malaya (11) Pritchard and Baker, 195Z Philippines (IZ) Rimando, 196z
Europe Austria (13) Dosse, 1957 Holland (14) Geijskes, 1939 Sicily (15) Di Martino, 1960 Spain (16) Baker, 1949
North America California (17) Pritchard and Baker, 195Z Cuba (18) Baker, 1949 Florida (19) Baker, 1949 Mexico (ZO) DeLeon, 1961 Puerto Rico (Z 1) Cromroy, 1958 Washington, D. C. (ZZ) Baker, 1949
Pacific Islands Hawaii (Z3) Baker, 1949
South America Argentina (Z4) Baker, 1949 Brazil (Z5) Rossetti, et al., 1959 Paraguay (Z6) Nickel, 1958 Trinidad (Z7) Pritchard and Baker, 195Z Venezuela (Z8) Knorr, ~t al., 1960
* Numbers after localities correspond to those on map in Figure 1. ---~------
Figure 1. Distribution map of Brevipalpus Eoenicis (Geijskes) .-J 8.
Also, papaya and passion fruit, two favorable hosts of ~ phoenicis, are well adapted and grown extensively in many of these areas.. In
1964 there were approxim.ately 1,350 acres in papaya and 250 acres in passion fruit in Hawaii. The climatic conditions in the areas where these crops are grown are warm, hUID.id, and conducive for year round reproduction of this false spider mite. The monthly maxim.UID. and minim.UID. temperatures for the period of this study, January, 1962 to
December, 1963, for Kaneohe, Oahu, where papaya is very often heavily infested by B. :phoenicis, for Kahului, Maui, where serious damage by this mite to passion fruit has occurred, and for Honolulu,
Oahu, where this mite is very common on many ornamental plants, are presented in Table II. The temperature in these areas seldom approaches the maxima and mini.m.a shown in Table II but usually fluctuates within a few degrees from the mean. In one such area, Wai manalo, Oahu, where ~ phoenicis outbreak was first seen on papaya, the mean temperature, the daily temperature range, and the annual temperature range have been recorded as 23.9°e, 7. 2oe, and 4.4oe, respectively (Ripperton and Hosaka, 1942). The hUID.idity condition in these areas is relatively high and seldom drops below 50 per cent.
B. phoenicis has not been recovered from areas above 2, 500 feet in elevation despite careful search on many kinds of plants. Tempera
ture is more variable in the upper areas than below (Ripperton and
Hosaka, 1942)0 In the upper areas, B. obovatus and B. californicus
were frequently encountered. TABLE II. MONTHLY MAXIMUM-1vfiNIMUM TEMPERATURES FOR HONOLULU AND KANEOHE, OAHU, AND FOR KAHULUI, MAUl, DURING 1962 AND 1963. i
Temperature °c Months 1962 1963 1962 1963 1962 1963 Max. Min. Max. Min. Max. Min. Max. Min. Max. Min. Max. Min.
Honolulu Kaneohe Kahului January 27.2 19.4 27.2 16.1 28.3 19.4 27.2 17.8 28.9 13.9 27.8 12.2 February 27.8 14.4 27.8 17.2 28.9 16.1 28.3 18.9 28.9 II. 7 29.4 14.4 March 26.7 18.9 28.3 17.2 27.8 17.8 28.3 18.3 30.6 15.0 30.6 15.6 April 28.3 19.4 27.2 18.3 28.9 20.0 28.3 20.0 31. 7 16.1 30.0 17.8 May 27.8 20.5 28.3 17.8 28.9 20.0 27.8 18.9 31. I 16.7 31. 1 16.7 June 28.9 21. 7 28.9 20.5 28.9 21. 7 28.3 21. 7 31. 7 16.7 31. 7 16.7 July 29.4 21. 1 28.9 21.7 28.3 21.1 28.9 21. 7 31. 7 18.3 31. 7 18.9 August 29.4 21. 7 30.0 22.2 29.4 22.2 30.0 23.3 31.7 '17.8 32.8 18.9 September 28.9 21. 1 29.4 20.5 29.4 22.2 30.0 22.8 32.8 16.7 31. 7 18.3 October 29.4 20.0 29.4 20.0 30.0 2.1.1 29.4 21.7 31.7 15.0 32.8 17.8 November 27.8 21.1 28.9 20.5 28.3 21.7 28.9 20.5 31.1 16.7 31.1 16. I December 26.7 15.6 28.3 18.3 27.8 18.3 28.9 20.0 29.4 12.2 29.4 13.9
AVERAGE 28.2 19.6 28.6 19.2 28.7 20.1 28.7 20.5 30.9 15.6 30.8 16.4
I. Readings furnished by the U. S. Weather Bureau.
.-.D 10.
HOST PLANTS
Phoenix sp., a greenhouse palm, was reported as the first host plant of.!h phoenicis in 1939. Since then, many different kinds of plants have been reported by several authors as infested by this species of mite in different parts of the world (Cromroy, 1958;
Pritchard and Baker, 1958; Baker and Pritchard, 1960; DeLeon, 1961; and Rimando, 1962). To date about 80 genera of plants have been listed as hosts of ~ phoenicis.
Previously, only seven species of plants have been recorded as hosts of B. phoenicis in Hawaii (Pritchard and Baker, 1952; and
Chilson, 1959), but some 39 species of plants belonging to 27 families were found infested during this present study. Papaya (Carica papaya
L.), passion fruit (Passiflora edulis f. £lavicarpa Degener), hemi graphis (Hemigraphis colorata (Bl.) Hallif.), :anthurium. (Anthurium. andraeanum. Lind.), and leInon (Citrus liJ:nonia Osbeck), are excep tionally favorable hosts of~ phoenicis. Only those plants which contained all stages of the Inite in sufficient num.ber s were included in the host list shown in Table ill. Although the list is by no means cOlnplete, it does show that B. phoenicis is polyphagous. Many Inore plants, belonging to the families listed in Table ill, are likely hosts of this Inite; however, it must be cautioned here that two other species
of false spider Inites. B. obovatus and B. californicus, which look
very much like ~ :e!:.0enicis coexist on m.any plants. There also TABLE m. LIST OF HOST PLANTS OF BREVIPALPUS PHOENICIS (GEIJSKES) IN HAWAII
Family Species Common Name
Acanthaceae Hemigraphis coloIata (Bl. ) hemigraphis Ballif.
Aizoaceae Sesuvium }.i.,jrtulacastrum L. carpet-weed
Anacardiaceae Mangifera indica L. mango
Apocynaceae Allamanda cathartica L. allamanda
Araceae Anthurium andraeanum anthurium lind.
Araliaceae Nothopanax guilfoylei panax (Gogn. and March.) Merr.
Bignoniaeceae Bignonia venusta Ker. orange trumpet vine
Cannaceae Canna indica L. canna
Garicaceae Carica papaya L. papaya
Compositae Eupatorium glandulosum Maui pamakani HBK. Bidens pilosa L. Spanish needle
Convolvulaceae Ipomoea batatas (L.) Poir. sweet potato Ipomoea pes-caprae (L. ) beach morning-glory Sweet
Cucurbitaceae Momordica balsamina L. balsam apple
Euphorbiaceae Acalypha wilkesiana copper leaf Muell. - Arg.
Liliaceae Cordyline terminalis (L.) ti Kunth
Malpighiaceae Malpighia glabra L. acerola 12.
TABLE III. Continued
Fanlily Species Common Name
Ma.lvaceae Hibiscus rosa-sinensis (L.) hibiscus Thespesia populnea (L.) mi1p._ Sol. .
Meliaceae SWietenia mahagoni (L.) mahogany Jacq.
MiInosaceae Prosopis pallida (Willd.) kiawe HBK
Myrtaceae P sidium guajava L. guava
Orchidaceae Dendrobium. ~ dendrobium Arundina. bambusuoHa bamboo orchid Lindl.
Palm<:+e Rhapis excelsa (Thunb.) bamboo palm Henry
Passifloraceae Passiflora foetida L. running pop Passiflora edulis f. yellow passion fruit flavicarpa Degener
Rubiaceae Coffea arabica L. coffee
Rutaceae Citrus :paradisi Mad. grapefruit Citrus sinensis (L.) Osbeck sweet orange Citrus limonia Osbeck lemon Murraya exotica L. mock orange
Sapindaceae Litchi chinensis Sonne litchi
Solanaceae Solanuxn sodoroeum. L. apple of sodorn
Verbenaceae Clerodendrum fragrans glorybower (Vent.) R, Br. var. pleniflorum Schau. Lantana. ca.mara L" lantana Lantana. montevidensis trailing lantana (Spreng.) Briq. 13. remains the possibility of recording plants which are merely accidental hosts because of the general prevalence of!!.. phoenicis in some areas.
Although ]h;phoenicis and !!.. obovatus are polyphagous and infest m.any kinds of plants in common, there are some plants which support only one of them. The garden violet, Yl2.!! odorata L., was found by Morishita (1954) to be a practical host for laboratory rearing of B. obovatus; however, in this study, it was found unsuitable for rearing .!!a. phoenicis. Likewise, 14 oboyatus was not able to re!1"0
duce on papaya which proved to be an excellent rearing medium for
~ phoenicis. These two plants, the garden violet and papaya, may
be used in the separation of mixed populations into pure cultures of
these two species of mites which coexist on many kinds of plants and
are extremely difficult to distinguish unless mounted and examined at
magnifications of 900X or higher. 14.
METHODS AND MATERIALS
Stock cultures of B. phoenicis were started from field collected specimens found infesting papaya in Manoa Valley, Oahu, Hawaii, on
April 25, 1962. The mites were mass reared on potted papaya plants, three to five months old, which were kept outdoors but sheltered from wind and rain. As needed, the mites we re transferred from these source plants to rearing media in order to study the various
aspects of the biology and control of this species of mite.
Since papaya of the Solo variety is of great economic itnport
ance and a favorable host plant of B. phoenicis, it was used to study
the life history of this species in the laboratory. Green papaya fruits
or sections thereof were used as rearing media for they remained in
fairly good condition long enough to allow the completion of a life cycle
and were easier to manipulate under laboratory conditions than other
types of media. Excised leaves and stems of most plants used as
rearing media required frequent changing due to rapid desiccation.
This was especially true when mites were reared on them at tempera
tures above 2SoC and at relative humidities below 60 per cent. The
necessity of frequent changes of the medium created a risk of injur
ing or 10 sing the mites while making the transfer s to fre sh medium.
When using papaya fruits under these adverse conditions, the entire
surface, except for the areas where the mites were allowed to feed,
was coated with paraffin. The paraffin film helped to prevent the rapid 15. desiccation of the fruits by reducing the surface area of transpiration.
For transferring mites from stock cultures to rearing m.edia, a human hair mounted on a wooden handle of a dissecting needle proved most satisfactory. Although the mites wer'e accidentally jabbed in the process of picking them up for transference, the hair was flexible enough so that no bodily harm was inflicted. The tip of
the hair was thrust beneath the venter of the mite from the caudal end until the entire body came to rest on the hair before lifting it off the
plant surface. SinCE:~. :phoenicis has a strong tendency to move in a
forward direction when disturbed, it was found best to pick up the mite
from the posterior so that the anterior end always faced the tip of the
hair. When the mite was picked up in this position, it crawled off the
hair readily onto the desired area of transference but when picked up
in the opposite position, posterior end facing the tip of the hair, the
mite invariably crawled up the hair towards the handle and made dis
lodging of it onto the plant surface difficult.
Whole fruits were used as rearing media for the life history
studies of B. phoenicis. lITanglefootll was used as a barrier to con
fine the mites on the fruits. All excess amounts of IITanglefootll were
scraped off with an edge of a microscope slide so that only a thin,
slightly tacky film was left along the inner margin and a thicker layer
left along the outer margin of the barrier. When liberal amounts of
"Tanglefoot" were deposited along the inner marginl• the active stages 16. of the mite invariably crawled into the material and died; however, when the excess was removed, they were prevented from being caught in it and also the remaining deposit was sticky enough to discourage them from walking over it. The thicker deposit of "Tanglefootlt on the outer margin of the barrier not only provided assurance against the confined mites from escaping but also prevented other mites from invading the premises of the individuals under observation.
The life history studies were begun with the egg stage. For each combination of temperature and humidity condition under which the life cycle of ~ phoenicis was carried out, the mites were confined in two ways, individually and in mass. When confined individually, tp.e
starting population of 100 eggs was placed on two fruits; 50 eggs to a fruit, and each egg was allocated an area of 1. 0 sq. cm. on the sur face of the fruits. When confined in mass., the 100 eggs were placed
on one fruit in four batches of 25 eggs each. Each batch of eggs was
confined within an area of 4.0 sq. cm. of the fruit surface. The result
ing larvae from these eggs were allowed to feed and to complete their
protonymphal and deutonymphal stages within the original confines
allocated to them earlier in the egg stage. Upon completion of the
deutonymphal stage, 50 newly emerged females from each tempera
ture and humidity combination studied were selected; 25 females from
those confined individually and 25 from those cmfined in mass, and
transferred to. fresh fruits. The females that developed from eggs 17. held individually and in mass were continued to be held in the res pective manner until completion of the life cycle. The eggs deposi ted by these females were counted and transferred from the fruit
surface onto 2. 0 cm. x 6. 0 cm. strips of adhesive tape on each ob
servational date. These eggs were exposed to the same temperature
and humidity conditions as the females which laid them to determine
thei.r 'h::otchability.
The fruits with the eggs confined on them were enclosed inside
of wide-mouth gallon jars and placed in constant tem];erature cabinets
for rearing. Within each jar, the fruit, together with a temperature
and humidity indicator (Airguide), were placed on top of a wire screen
platform which was elevated about 8.0 cm. above the bottom of the
jar (Fig. 2). Also, in the bottom of each jar, 650 cc. of a saturated
salt solution was added in order to maintain·the desired level of
humidity within the closed system. The salts used to obtain the follow
ing levels of relative humidity: 25 to 30 per cent, 65 to 70 per cent,
and 85 to 90 per cent, were potassium acetate, ammonium nitrate,
and potassium nitrate, respectively.
A modified refrigerator and a commercial incubator were used
as temperature cabinets. These cabinets were held in an air con
ditioned room where the temperature varied between 2loe and 240 e
and humidity between 60 and 70 per cent. The modified refrigerator
was used for temperatures below Z5 0 e and the incubator for 180
'"
Figure 2 0 Rearing unit used in the constant temperature and humidity experiments. 19. temperatures of 2SoC and above. Both of these cabinets were equipped with thermo-regulators and thermostats of:l: O. SoC sensi tivity. The thermo-regulator of each cabinet was adjusted and set to the desired constant temperature with the aid of thermocouples and a potentiometer. A mercury-in-glass thermometer was placed inside each cabinet and this, together with the temperature and humidity indicators enclosed within the jars, were referred to each day to in sure that the relative humidity and temperature were maintained relatively constant throughout the life cycle of the mites.
Once the mites were placed in the cabinets, they were taken out only briefly whenever necessary to observe and record the various life history events. Those mites which were confined individually were taken out from the cabinets at least three times daily for about
lO minutes each time in order to obtain the necessary data for deter mining the stadia of the different life stages, the preoviposition period and fecundity of the females, and the other aspects of the life history.
Those mites which were held in mass were taken out not more than once a week. Comparison of the survival populations from those con fined individually and in mass revealed that isolation as well as the frequent removal of the individually confined mites from the constant
temperature and humidity conditions to laboratory conditions had no
significant effect on the survival potential of~ phoenicis. 20.
Sections of papaya fruit embedded in agar were used as rearing media for the chemical control studies of B. phoenicis. This type of rearing medium as shown in Figure 3 was prepared as follows: A
2 per cent agar solution was heated to the boiling point and then poured into an aluminum foil tart plate, 8.0 cm. in diameter, until filled to a depth of approximately 1. 0 em. After the agar solidified, a piece of papaya fruit, about 5.0 cm. in diameter, was placed cut surface down in the center of the plate. Then, more agar solution, first cooled to
450 C, was poured until about one-half of the original surface of the papaya section became embedded. The agar provided moisture and kept the papaya section fresh for two weeks under conditions of 21 0 C
to 240 C and 60 to 70 per cent relative humidity and also served as an
effective escape barrier against the active stages of B. phoenicis.
Mites were transferred from the stock cultures onto rearing media
of thi s type a day prior to subjecting them to the different pesticides
shown in Table VI. Twenty-five females were placed on each plate
and four such plates, or 100 individuals, made up each treatment.
Of the active stages, only the adults were selected for exposure to
the different treatments for in preliminary studies they proved to be
more tolerant of these pesti,cides than the larvae and nymphs.
A settling mist tower which was improvised by Sanchez and
Sherman (1963) was used to apply the pesticides. The four plates of
each treatment were placed on the turntable which revolved around a ¥igure 3. Rearing unit used in the chemical control studies of BrevipalpuB ~~ (Geijskes) N t-4 • 22.
Venturi tube through which 5.0 cc. of a pesticide was blown under pressure of about 50 p. s. i. into the tower as a mist. The mist was allowed to settle for three minutes onto the plates. These plates, with the treated mites on them, were held for two weeks in an air conditioned room where temperature ranged from 210 C to 240 C and relative humidity from 60 to 70 per cent. Mortality records of the mites were taken on the first, third, fifth, and seventh day after treatment, and also on the seventh day all of the living females and
eggs present on the plates were counted. The living females were
removed at that time but the eggs were left in situ until hatching to see
if the pesticide residues on the media were still toxic to kill the larvae
which emerged 10 to IS days after the application of the pesticides.
In addition to the tests with the adults, eggs of B. phoenicis were
also subjected to the different pesticides shown in Table Vill, using
the dip method. Only the higher concentrations of most of the pesti
cides were used because the lower concentrations gave no significant
kill of B. phoenicis eggs. Each treatment consisted of four repli
cations of 25 eggs each, or a total of 100 eggs. They were placed on
2.0 cm. x 6.0 cm. strips of adhesive tape and dipped for a minute in
the various pesticides. These treated eggs were held for three weeks
in an air-conditioned room to see if the pesticides had any ovicidal
effect.
Since the effects of some of the pesticides on papaya were 23. 24.
DESCRIPTION OF ~IFE STAGES
The life stages of ~ phoenicis include the egg, larva, proto nym.ph, deutonym.ph, and adult. Both sexes are present, but m.ales are scarce and have not been found in many parts of the world where this species exists.
lh: phoenicis is a very variable species, but it Can be readily distinguished in the adult stage from. the other mem.bers of the genus by having five pairs of dorsolateral hysterosom.al setae and two sensory rods on tarsus IT (Fig. 9B). The larvae and nym.phs also have five pairso£ dorsolateral hysterosom.al setae but, unlike the adults, they have only one sensory rod located posteriodistally on tarsus IT. Morphologically, the im.m.ature stages of.!h phoenicis closely resemble those of.!h obovatu.s, and like them., they are sub ject to considerable variation in the size and shape of some of the dorsal setae. The num.ber and arrangem.ent of the setae on the dorsum. of idiosom.a of the larva, protonym.ph, and deutonym.ph con form to those of the adult and to the genus Brevipalpus ~'pritchard and Baker, 1952). Twelve pairs of setae are preaent on the dorsum.;
three pairs on the propodosoma and nine pairs on the hysterosom.ao
The location and nom.enclature of these setae are shown in Figure 4.
The size and shape of the dorsal setae of most larvae and nym.phs on papaya are like those shown in the respective illustrations (Figs. 6,
7, and 8), and as described in the sections on the life stages below. MEDlOVENTRAL if> >:t 7' PROPOOOSOMAI.. :::b DOflSAL PROPClO ANTERIOR MEDlOVENTRAL y,... METAPOOOSOMAL r- ,'\. <~ HUIll£RAL POSTERIOR MEDlOVENTRAL 9'i:,'S \. METAPOOO8OIlIAL > 'i t. ~ DOR8OC£NTlW. 1fYSTEROSOMAI.S VENTRAL PLATE ,.., f/ I .it /'I I.>W ,..,~ DORSOUIT'ERAL GENITAL PLATE /Aql h I \0 :'_ HYSTEROSOMALS ANAL PLATE ' \ \1\. 'i~ ... ( \\1 ~'Je....--' AIB ~igure 4. Outline drawing of Brevipalpus phoenicis (Geijskes) female showing the location and nomenclature of the setae and plates. Ventral aspect (A) and dorsal aspect (B). N 1.11 • 26. Of the dorsal setae, dorsolateral hysterosomal setae I and II, and dorsocentral hysterosomal setae ill are most variable in size and shape. These vary from a tiny, serrate setae to large, broadly lanceolate, serrate setae similar to dorsal propodosomal setae II and ill. larvae and nymphs with these large setae were more frequently encountered on passion fruit and bamboo palm than on papaya. DeLeon (1961) found nymphs of most Mexican specimens of.!!:. phoenicis with the large dorsolateral hysterosomal setae I and II, and in three collections, nymphs with the dorsocentral hysterosomal setae nearly as large as the dorsolateral setae. The location and nomenclature of the setae on the venter of the idiosoma are shown in Figure 4. The number of setae on the venter is not constant but increases from four pairs on the larva, five pairs on the protonymph, seven pairs on the deutonymph to eight pairs on the adult. These additions take place in the hysterosomal region of the body. A pair of medioventral opisthosomal setae is present in the two nymphal and adult stages but not in the larval stage. The medio ventral propodosomal setae, which are present in the larval, nymphal and adult stages, and the posterior medioventral metapodosomal setae, which are present only in the deutonymphal and adult stages, are filamentous and smooth. The remaining ventral setae are short and smooth. The following descriptions of the life stages are based on 27. individuals reared on papaya. All observations and measurements were made on at least 25 individuals of each stage. Measurements were taken on living spedmens since mounted ones often undergo con- siderable distortion in size. Mites were placed on adhesive tape, to keep them quiescent, and measured under 300 times magnification using incident light. The width measurements of the larvae, nymphs, and adults wer e taken at the level of the humeral setae, and the length taken between the distal ends of the rostrum and opisthosoma (Table IV). The meaSUremeI:lts shown for the larva, protonymph, and deutonymph were taken on the inactive phases and represent the average maximum size attained by individuals in the respective sta- dium. The average minimum size for each stage is the same as the measurements given for the stage preceding it. TABLE IV. AVERAGE MEASUREMENTS OF THE LlFESTAGES OF BREVIPALPUS PHOENICIS (GEIJSKES) Length (mm) Width (mm) Stage Mean S. D. Mean S. D. Egg 0.108 0.004 0.070 0.004 Larva, inactive 0.171 0.005 0.109 0.004 Protonymph, inactive 0.232 0.005 0.140 0.004 Deutonymph, inactive 0.308 0.008 0.163 0.005 Adult, female 0.308 0.007 0.163 0.004 S. D. = Standard deviation. 28. The egg (Fig. 5) is elliptical and about 0.100 to 0.116 mm. long and 0.060 to 0.080 mm. wide, averaging 0.108 I:. 0.004 mm. in length and 0.070 I: 0.004 mm. in width. It is light orange, soft, and very sticky when first laid. At this time, the egg adheres readily to any surface it comes in contact with and attempts to remove it usually result in its breakage. After a few minutes of exposure to air, it be comes firm and bright reddish orange. The chorion is thin, trans parent, and made up .of at least two layers. The outer layer is drawn out to a fine stipe on the end of the egg which emerges last from the ovipositor. This stipe is variable in length and is often missing for it can be easily broken off by the mites trampling over it. The stipe is also inconscpicuous in some cases for it bends back and adheres to the surface of the main portion of the egg. When the egg is viewed under 450 times magnification with incident light, many close set irregular striae are visible on the chorion; however, when it is mounted in Hoyer's medium, the outer layer together with the stipe are dissolved away and the clear, smooth, inner layer becomes exposed. The protoplasm, which is translucent light orange when the egg is first laid, completely fills the inside of the chorion and is in close contact with it. With the advancement of the incubation period, a space between the developing embryo and the chorion is formed. The egg becomes opaque white a day before eclosion. The larva and its 29. ,Figure 5. Egg of Brevipalpu6 phoenicis (Geijskes). Enlarged approximately 409 times. 30. bright red eyes are visible through the translucent white chorion at this time. larva The hexapod larva (Fig. 6) is bright orange-red when newly emerged and 0.128 to 0.140 mm. long and 0.080 to 0.096 mm. wide, averaging 0.135 I:. 0.004 mm. in length and 0.088 I:. 0.005 mm. in width. When fully grown and ready for molting, it is opaque orange and 0.171 I:. 0.055 mm. in length and 0.109 I:. 0.004 mm. in width. Two pairs of red eyes are present on the lateral margins of the pro podosoma. EKcept for the suture between the propodosoma and the hysterosoma, and the irregular, folds along the lateral margins of the idiosoma which gradually disappear as the larva grow, there are no characteristic integumental markings on the dorsum. The integument on the venter of the idiosoma, however, has regular parallel striae; transverse on the propodosoma and anterior portion of the opisthoso ma, and longitudinal on the metapodosoma and laterad of the anus. On the dorsum, the propodosomal setae II and ill, humeral setae, and the dorsolateral hysterosomal setae ill and V are serrate, broadly lanceolate, and O.OIl to 0.014 mm. long and 0.004 mm. wide. The dorsolateral hysterosomal setae IV are filiform, 0.042 mm. in length, and the remaining dorsal setae are serrate and short, less than 0.004 mm. (Fig. 6). 31. ;Figure 6. larva of Brevipalpus phoenicis (Geijskes). Dorsal aspect. Enlarged approximately 364 times. 32. On the venter of the idiosoma, four pairs of pilose setae are present; a pair of long medioventral setae on the propodosoma, a pair of short medioventral setae on the metapodosoma, and two pairs of short anal setae on the opisthosoma. Protonymph The protonymph (Fig. 7) differs from the larva essentially in being larger and in possessing four pairs of legs. Scattered light green, orange, black, and yellow patches, resulting from accumu lations of food and waste matter inside the body, can be seen through the translucent integument of the idiosoma. The protonymph grow s from a minimum size of 0.171 mm. to a maximum size of 0.244 mm. in length and from 0.109 mm. to O. 148 mm. in width, averaging 0 ..2'32 I: 0.005 mm. in length and 0.140 ~ 0.004 mm. in width as an inactive protonymph. Except for the suture between the propodosoma and hysterosoma and the few folds which gradually disappear as the protonymph grows, no characteristic markings are present on the integument of the dorsum. On the venter, however, there are regular parallel integumental striae running transversely across the central portion of the idiosoma with the ends bending longitudinally to the lateral margins. Longitudinal striae are present between the medio ventral setae of the propodosoma and the base of the gnathosoma. On the dorsump the propodosomal setae II and ill, humeral setae, and the dor solateral hysterosomal setae ill, IV, and Vare 33. Figure 7. Protonymph of Brevipalpus phoenicis (Geijskes). Dorsal aspect. Enlarged approximately 234 times. 34. broadly lanceolate and serrate. All of them are about the sam.e size, 0.014 mm. to 0.016 rr..m. long and 0.006 rom. at the widest part. The remaining setae: propodosom.al setae I, dorsolateral hystero somal setae I and II, and dorsocentral hysterosomal setae I, II, and m, are serrate and very small, less than O. 004 mm. long (Fig. 7). On the venter of the idiosom.a, there are five pairs of pilose setae; one pair of medioventral setae on the propodosoma, metapodo soma, and the opisthosoma. The setae on the propodosoma are long, I 0.028 mm. to 0.031 mm.., while those on the m.etapodosom.a and opisthosoma are short, O. 004 mm. to o. 006 rom. Two pairs of setae, similar in length to the medioventral opisthosomal setae, are present on the anal sc1erites. Deutonymph The deutonymph (Fig. 8) is similar to the protonymph in color, dorsal chaetotaxy, and in the pattern of the striae on the venter of the idiosoma. In this stage, two additional pairs of pilose setae are present on the venter of the idiosoma: a pair of long posterior medio ventral metapodosomal 'Setae, 0.031 mm. long, and another pair of short setae, 0.006 mm., near the anterior margin of the anus similar in size and shape to those located below on the anal sc1erites. When fully grown and ready to molt, the size of the deutonymph ranges from 0.292 mm. to 0.324 mm. long and 0.156 to O. 168 mm. wide, averaging Figure 8 9 Deutonym.ph of Brevipalpus :phoenicis (Geijskes). Dorsal aspect (left). Ventral W aspect (right). Enlarged approximately 263 times. •\J1 36. 0.398 1:. 0.008 m.m.. in length and 0.163 1:. 0.005 mm.. in width. Female The female (Fig. 9) ranges in size from 0.288 rom. to 0.312 m.m... in length and 0.156 rom. to 0.176 mm.. in width, averaging 0.302 t 0.007 rom. in length and 0.162 t 0.004 rom. in width. The body coloration of the females is very variable. Differences in age, food, and temperature conditions have great influence on body color ation. In newly emerged females, the area between the red eyes is bright orange and the remainder of the idiosoma is translucent light yellow with a few brownish patches occurring mediolaterally on the hysterosoma. When feeding begins, a conspicuous black pattern in the shape of an "Hit appears on the idiosoma (Fig. 10E to H). The black pattern enlarges, coalesces, and covers almost the entire idiosoma of some individuals (Fig. 101). This black pattern gradual ly disappears and the females once again assume a uniform carmine body color a few days prior to death. Females reared at a tempera ture of 300 C have a uniform carmine body color and those reared at 200 e and 250 e usually have the black patterns on the idiosoma. Females on passion fruit are mostly reddish orange and have less variations in body coloration than those on papaya (Fig. lOA to 1). On the dor sum, the integument has reticulations mediolaterally on the propodosoma and hysterosoma. A pair of pores are present.. Figure 9. Female of Brevipalpus phoenicis (Geijskes). Dorsal aspect (A) palpus (B) tarsus IT (left). Ventral aspect (right). Enlarged approximately 300 times. UJ -.:I • 38. E Figure 10. Variation in color patterns of females of Brevipalpusphoenicis (Geijskes). 39. mediolaterally on the propodosoma and metapodosoma. Propodo- somal setae I, II, and ill, humeral setae, and do-rsolateral hystero- somal setae I, II, ill, IV, and V are narrowly lanceolate, serrate, and less than 0.010 mm. in length. The three pairs of dorsocentral setae are minute at;ld setiform. On the venter of the idiosoma, the reticulations on the ventral plates and area directly anterior to them are wider than long and those laterad to them are longer than wide. Eight pairs of pilose setae are present: a pair of medioventral propodosomal setae, two pairs of medioventral metapodosomal setae, a pair of setae on the ventral plate, and two pairs each on the genital and anal plates. The medioventral propodosomal and the posterior medioventral metapo- dosomal setae are filamentous and about 0.070 mm. long. The pair of anterior medioventral metapodosomal setae and those on the ven- tral and genital plates are similar in length and about one-fifth the length of the posterior medioventral metapodosomal setae. The anal setae are the shortest of the setae on the venter and about one-half the length of the genital setae. Male The male (Fig. 11) is wedge-shaped in outline and flattened in profile. The idiosoma is reddish and has no black marldngs like those on the females. 40. On the dorsum, two transverse sutures demarcate the propo dosomal, metapodosomal, and the opisthosomal regions of the body. The integument has rather even reticulations mediolaterally and ir regular reticulations mediodorsally on the propodosoma, metapo dosoma, and the opisthosoma. A pair of pores is present on the propodosoma and the metapodosoma. The dorsal chaetotaxy is similar to that of the female. On the venter of the idiosoma, reticulations are present medio laterally along the bases of attachments of legs il, ill, and IV, on the opisthosoma, and medioventrally along the posterior margin of the metapodosoma. The medioventral propodosomal and the posterior medioventral metapodosomal setae are filamentous and very long, 0.070 mm. or more in length. The anterior medioventral metapo dosomal and the medioventral opisthosomal setae are pilose and very short; the former about one-fifth and the latter about one-sixth the length of the posterior medioventral metapodosomal setae. Three pairs of short, very narrowly lanceolate, and serrate setae are present on the genito-anal sc1erites. Figure 11. Male of Brevipalpus phoenicis (Geijskes). Dorsal aspect (A) palpus (left). II:>- Ventral aspect (right). Enlarged approximately 300 times. .J-004 42. LIFE HISTORY The following is the life history of B. phoenicis based on infor- mation ob~ined from laboratory rearings conducted under different levels of relatively constant temperature and humidity conditions. These two physical factors have been shown to greatly influence the developmental and reproductive rates of several species of mites (Morishita, 1954; Boudreaux, 1958; and Nickel, 1960). The purposes of this life history study were to determine the approximate tempera- ture and humidity combinations which favor natality and their ranges which the various stages of B. phoenicia can tolerate. It is hoped that the information obtained from this study will be helpful in better understanding the other biological aspects of this mite. Food and space were kept constant and provided in adequate amounts so as to minimize intraspecific competition for them. In addition, other factors that could influence the life history of ~ phoenicis, such as natural enemies and interspecific competition, w:ere excluded in the present study. Egg Stage The egg is deposited in any position in cracks, crevices, exuviae, and other protected niches on the plant surface. It is laid singly but since the females tend to reuse the same ovipositional sites, many eggs are often clustered together. These clusters of bright reddish orange eggs are more readily seen with the unaided eye than the other I'··.···.·········, stages of the mite. When an egg is ready for ec1osion, one end 01' ~! becomes swollen due to the larva pushing against the inner wall of the chorion with its rostrum. With incident light and at magnifir3tions of 300X or higher, the larva can be seen repeatedly clawing tn€' h~!lel" waH of the chorion with its front pairs of legs as if tTying to malt€' ing for emergence. After a while, the chorion splits ~l"tlv around on". end of the egg at approximately the level of clawing. The larva &t~_ '':>ll out one of its front legs through the split and uses it to enl~u'ie the opening further. The larva then emerges anterior end first a.nd in itw: process pushes aside one end of the chorion which remains conflened like an "hinged door" to the remainder of the chorion. The empty transparent chorion remains attached to the plant surface for a long time unless forcibly removed. The eggs were found to be greatly affected by the prevailing tt>!1:;- perature and humidity conditions. Their incubation period and ha.td~·· bility varied significantly between the different temperatures inespE'i.: tive of humidity conditions; however, between humidity levels of 63 t(.) 70 per cent and 85 to 90 per cent at a given temperature, they wert':' essentially the same (Table V). Within each temperature. hatchabil.ity was lowest at the 25 to 30 per cent humidity level and the incubation period about a day longer than at the higher levels of humidity. The minimum incubation period was 8.0 days at 30°C in combination with 65 to 70 per cent relative humidity and the ma.'timum 24.8 days at ZOoC in combination with 85 to 90 per cent relative humidity. Under the 43. stages of the mite. When an egg is ready for eclosion, one end of it becomes swollen due to the larva pushing against the inner wall of the chorion with its rostrum. With incident light and at magnifications of 300X or higher, the larva can be seen repeatedly clawing the inner wall of the chorion with its front pairs of legs as if trying to make an open ing for emergence. Mter a while, the chorion splits partly around one end of the egg at approximately the level of clawing. The larva sticks out one of its front legs through the split and uses it to enlarge the opening further. The larva then emerges anterior end first and in its process pushes aside one end of the chorion which remains connected like an "hinged door" to the remainder of the chorion. The empty transparent chorion remains attached to the plant surface for a long time unless forcibly removed. The eggs were found to be greatly affected by the prevailing tem- perature and humidity conditions. Their incubation period and hatcha bility varied significantly between the different temperatures irrespec tive of humidity conditions; however, between humidity levels of 65 to 70 per cent and 85 to 90 per cent at a given temperature, they were essentially the same (Table V). Within each temperature, hatchability was lowest at the 25 to 30 per cent humidity level and the incubation period about a day longer than at the higher levels of humidity. The minimum incubation period was 8.0 days at 300 C in combination with 65 to 70 per cent relative humidity and the maximum 24.8 days at 200 e .in combination with 85 to 90 per cent relative humidity. Under the TABLEV o EFFECT OF TEMPERATURE AND HUMIDITY ON THl (GEUSKES) Stage R E LA TI V E &: 25 to 30 Per Cent 6! Temperature Duration (days) I °c N Range MeantS. D. N Rani Starting N 100 100 (Egg) ~ 20 5 21.4-23.4 23.0iO.2 67 19.8· 25 8 8.7-12.6 11. 1~I. 1 88 9. I· 30 0 27 8. o· Larva 20 No survivors beyond 65 9.8· 25 egg stage 88 4.8· 30 26 3. 1· Protonymph 20 59 7.8· 25 87 4.5 30 26 2.6 Deutonymph 20 50 3.5 25 85 4.7 30 25 3.5 Immature Stage Egg to Adult 20 50 17.4 25 85 23.1 30 25 16.5 Adult, Female Preoviposition 20 25 3.2 25 25 2.1 30 16 7.0 Fecundity 20 25 5 25 25 41 30 25 0 Longevity 20 25 13.4 25 25 21. C 30 25 3. e 44. ~ ON THE,DIFFERENT STAGES OF BREVIPALPUS PHOENIGIS lVE HUMIDITY 65 to 70 Per Cent 85 to 90 Per Gent Duration (days) Duration (days) Range MeantS. D. N Range MeantS. D. [) 100 7 19.8-24.6 22.2Jl.l 65 18.8-24.8 22.61:.1. 1 8 9.1-13.0 9.4~0.6 85 8.0-12.9 9.4tO• 8 7 8.0- 9.0 8.2/:.0.4 29 7.8- 9.2 8.4tO• 9 5 9.8-12.4 10.5~0.7 62 9.5-11.9 10.4tO• 5 8 4.8- 8.9 6.71:.0.8 83 5.8- 7.8 6.5~0.7 6 3.1- 4.5 3.6.J.0.2 27 3.6- 4.5 3.71:.0.4 9 7.8- 9.5 8.21:.0.7 60 7.7-10.2 8.4/:.0.9 7 4.5- 9.6 6.31:.0.9 83 4.0- 9.6 6. 5~1. 1 6 2.6- 3.7 3.11:.0.4 27 2.7- 3.5 3.0JO.5 0 3.5- 4.1 7.51:.0.9 58 2.7,- 4.1 7.3tI.l 5 4.7- 9.1 6.8~0.8 83 4.3- 8.2 6.91:.0.5 5 3.5- 3.9 3.71:.0.5 26 3.8- 4.0 3.91:.0.1 17.4-20.4 48.81:.1.5 58 45.4-50.5 47. 7f:.2. 5 23.1-34.5 29.31:.0.4 83 22.0-33.0 29.31:.1.2 16.5-19.0 18.6~0.5 26 16.8-19.8 18.11:.0.2 :5 3.2- 9.5 5. 7tI. 4 25 3.5- 9.0 6.2/:.2.3 ~5 2.1- 6.7 3.51:.0.9 25 2.3- 6.5 3.71:.0.6 [6 7.0- 8.0 7.31:.0.2 14 7.5- 9.0 8.0~0.3 ~5 5-29 10.61:.4.5 25 5-20 12.4J5.6 ~5 41-73 57r51:.10.7 25 8-68 53.3t7.5 ~5 0-19 6.41:.2.4 25 0-17 7.5~1.7 ~5 13.4-72.3 45.8/:.9.7 25 15.0-70.3 47.01:.12.1 ~5 21.0-44.0 34.81:.6.0 25 25.3-50.0 34.51:.3.5 ~5 3.8-20.8 10. 5t3~ 7 25 4.5-12.0 7.5J2.0 45. foregoing conditions, however, only a few of the eggs hatched; 27 per cent under the former and 63 per cent under the latter conditions. Optimum hatch of 88 per cent was obtained at 25°C in combination with 65 to 70 per cent relative humidity; however, the average incu bation period in this case was slightly longer than that at 300C with the same level of humidity but the majority of the eggs hatched in 9.4:1: 0.6 days or less than one-half the time required by those subjected to 20°C. Some eggs hatched at 20°C and 25°C in combination with all three levels of humidity, but at 30°C, hatching occurred only at the 65 to 70 per cent and 85 to 90 per cent levels and none hatched at the 25 to 30 per cent level. None of the eggs hatched when exposed for several days to con stant temperatures below 20°C and above 30°C in combination with either high or low humidity. The eggs maintained the shape and color of freshly laid ones for about a month at temperatures below 20°C but they became shriveled and opaque white in about four days at tem peratures above 32°C, especially when humidity was low. Although continuous exposure of eggs to 20°C and 30°C caused considerable reduction in hatchability, an exposure of 24 hours first to either of these temperatures and then maintaining them at 25°C with 65 to 70 per cent relative humidity had no detrimental effect on hatchability. However, when temperature was decreased below 20°C and increased above 30°C, short exposures caused hatchability of eggs 46. to decline gradually in the former and abruptly in the latter case. Hatchability of eggs which were first exposed to the different high and low temperatures for 24 hours and then maintained at 250 C in combi nation with 65 to 70 per cent relative humidity, declined from 89.5:1: 3. 0 per cent at 300 C to 45.0:1: 5. 5 per cent at 320 C to O. 0 per cent at 340 C or a 100 per cent reduction in a temperature change of only four degrees; but at the low temperatures, it declined from 87.5 :I: 4.5 per cent at 200 C to 41.0 :I: 4.5 per cent at 150 C to 27.5 :I: 6.0 per cent at 100 C or a reduction of some 68 per cent in ten degree change in tem perature. Immature Stages The larva, protonymph, and deutonymph each spends about one half of its stadium as an active and one-half as an inactive individual. Feeding, growth, and limited dispersion take place during the active phase and transformation into the subsequent stage during the inactive phase. Prior to becoming inactive, the mite assumes a characteristic position. The chelicerae are fully extruded and inserted into the plant tissue; the front two pairs of legs are extended straight forward and drawn close to each other; and the posterior legs, one pair in the case of the larva and two pairs in the case of the nymphs, are extended straight backwards and held close to the sides of the opisthosoma. This characteristic position was assumed to be the ending of the active and the beginning of the inactive phase of each stage. Although the 47. chelicerae are inserted in the plant tissue during the inactive phase, they are not used for obtaining nourishm.ent but are used for an-chor ing the body in place. Besides using the chelicerae for anchoring, an adhesive substance is apparently secreted by the mite just prior to becoming inactive for the entire ventral surface of the body is fastened to the plant surface as though glued and prying is needed to dislodge an inactive mite. Ecdysis progresses normally even though such a mite is dislodged soon after becoming inactive but the sub sequent stage has some difficulty in freeing itself from the exuvium at the time of molting. When an inactive larva is mounted in Hoyer's medium and examined under 300X or better magnification with trans mitted light, the outline of the developing protonymph can be seen inside the exoskeleton of the larva. Legs I, II, and III of the proto nymph are held inside the corresponding legs of the larva but since the latter has only three pair s of legs, legs IV of the former are held free along each side of the opisthosoma. The habits of all the immature stages are similar except feed ing, growth, and dispersion become more pronounced with. the passing of each stage. The newly emerged larva wander s in the im mediate vicinity of the chorion from which it has emerged for about an hour before commencing to feed while the newly emerged proto nymph and deutonymph move further away from their exuviae and com.m.ence feeding almost im.rn.ediately. The feeding damage done by 48. the larva is hardly noticeable but that inflicted by the later stages is readily discernible for the imm.ediate area around each feeding puncture becomes discolored and blisterlike soon after the insertion of the chelicerae (see page 57 for further descriptions of feeding dam.age). The larvae and nymphs seldom leave the area where they had emerged from the egg stage. They feed avidly and grow rapidly during the active phase and undergo transformation just as rapidly dur ing the inactive phase when environmental conditions are favorable. The temperature and humidity conditions favoring egg hatch also proved suitable for larval and nymphal survival. At 250 C in combi.. nation with 65 to 70 per cent relative humidity, conditions under which optimum hatchability was obtained, the majority of the newly emerged larvae successfully passed through the three immature stages in 19.8 f:. 0.9 days. Development of the immature stages from egg hatch to adult emergence was most rapid at 30°C, 10.6 t 0.3 days, and slowest at 20oC, 27.3 t 1.7 days. Some individuals successfully reached the adult stage under constant temperatures of 200C, 25°C, and 30°C in combination with either 65 to 70 per cent or 85 to 90 per cent relative humidity, but none survived beyond the larval stage when humidity was 25 to 30 per cent (Table V). Except for the temperature and humidity combinations of 25°C with 65 to 70 per cent and 85 to 90 per cent at which more than 80 per cent of the starting population suc cessfully completed the egg, larval, and the nymphal stages, the other 49. combinations caused high larval mortality in addition to the low egg hatch so that less than 35 per cent of the starting population reached the adult stage. But once passed the larval stage, the protonymphs reached the adult stage without much mortality for the nymphs were more tolerant of the adverse conditions than the earlier stages (Table V). o Prolonged exposures to temperatures above 30 e and below 0 20 e were fatal to the immature stages regardiess of humidity condi- tions. The larvae died within two days after being exposed to 320 e, whereas they became motionless, ceased to develop beyond that stage, and remained alive for at least 10 days when exposed to 180 e. Some larvae remained alive for as long as a week at temperature as low as 100e and when transferred to favorable temperature and humidity conditions, 250 e in combination with 65 to 70 per cent relative humidity, they continued development. Adult Stage The adult stage was reached in I~. 6 i. 0.5 days at 300 e and in 48.8 I:. 1.5 days at 200 e after the eggs were laid. At these extremes in temperature, only few of the starting population of eggs success- fully reached the adult stage despite favorable humidity conditions (Table V). Completion of the life cycle was not possible when tem perature was above 30 0 e and below 200 e regardless of humidity conditions, and when humidity was only 25 to 30 per cent regardless 50. of temperatur'e conditions. Survival was highest at 250 C in cOUlbi nation with either 65 to 70 per cent or 85 to 90 per cent relative humidity as 85 and 82 individuals reached the adult stage out of each of the starting population of 100 eggs, respectively. All of the adults that were reared from the egg stage under the different temperature and humidity combinations were females, and thus, the discussion that follows on the various life processes of the adult stage is on the female sex. Preoviposition Period: The female starts to feed soon after freeing herself from the deutonyxnphal exoskeleton and must feed before egg laying can comm.ence. This period between emergence and deposition of the first egg, referred to as the preoviposition period, wa,s as shown in Table V for the different temperatures in combination with 65 to 70 per cent and 85 to 90 per cent relative hwnidity. Although the durations of all life processes discussed thus far, such as eclo sion, ecdysis, life cycle, etc.: were shortest at 30oe, the preovi position period was longer at this temperature than at 200 e and 250 e. Moreover, continuous exposure to 300 e probably affected the reproductive physiology in the early stages of development for many of the females failed to lay any eggs even though they were trans ferred to more favorable temperature and humidity conditions soon after reaching the adult stage. Females in which the earlier stages 51. were exposed to constant temperature of 250 C, however, started to lay eggs earlier when exposed to 300 C soon after becoming adults than those kept continuously at 250 C from the egg stage to the end of the preoviposition period. Oviposition: When ready for oviposition, the female locates a suit able site such as an exuvia, crack on the plant surface or a bud axil for depositing the egg. She first examines and cleans out all debris from the site with the front pair of legs, turns herself 180 degrees so that the tip of the opisthosoma now is in contact with the ovipositional site, and then deposits the egg after about a minute of alternate con tracting and expanding of the body. After depositing an egg the female leaves the oviposition site and resumes feeding in its proximity until the next egg is ready for deposition some six hour s later at the earli est, at which time she usually returns to the former site to deposit it. Because of this habit of returning to the same site for oviposition and since many females frequently oviposit in a common site simul taneously, several eggs are massed together even though only one egg is laid per individual during an extended duration. The female seldom wandered afar but remained within the confines of the original area in which she was reared as long as food was ample and suitable. When intraspecific competition for food and space became intensive due to overcrowded conditions, the females emigrated to uninfested 52. parts of the same plant or to other plants and continued feeding and oviposition. The number of eggs laid by the females varied greatly with temperature differences when humidity was kept constant (Fig. 12 and Table V). At 250 C, all of the females began laying eggs and con tinued to lay from one to four egg s per day per individual during their life span. One of the females laid a maximum of 76 eggs in 42 days of existence and these were deposited equally during the day and night without any peak periods of oviposition. Out of the 562 eggs laid during a 24-hour period by 300 females which were kept under con stant temperature of 25uC in combination with 65 to 70 per cent relative humidity, 271 were deposited between 8:00 a.m. and 8:00 p. m. and 291 between 8:00 p. m. and 8:00 a. m. These eggs were de posited uniformly throughout the day and night without any peak hours of oviposition. Oviposition was very irregular at 200 e and 300 C and it ceased at temperatures below and above these temperatures, res pectively. All of the females laid some eggs at 200 e but over 50 per cent of them failed to lay eggs at 30oe. At these two temperatures, the number of eggs laid per female was less than one-fifth the num ber laid at 250 C. When gravid females were subjected to tempera ture of 18oC, they laid no eggs as long as they were held at this temperature, but when returned to 25°C, they commenced to lay eggs again after 8 to 10 hours. Some females survived exposure to 53. Z 2 3 4 II 8 7 8 9 10 WEEKS ,Figure 12. Mean number of eggs laid per week by four starting populations of 25 Brevipalpus phoenicis females. 54. constant temperature as low as 100 C for 23 days and wh.en returned to more favorable conditions, 25°C and 65 t?_ 79 per cent relative humi dity, they started to lay eggs after a day. Longevity: Some of the more obvious factors which affected the longevity of the adults were food, temperature, and humidity. When food was withheld, the adults died from. starvation within three days. The adults were m.ore susceptible to temperature changes than to humidity changes and they tolerated the changes better than the im. mature stages. The adults lived longer under tem.perature conditions below 25°C than above it (Fig. 13 and Table V). The average longevi ty was 47.0 t 12.1 days at 20°C but only 7.5 t 2.0 days at 30°C in com.bination with 85 to 90 per cent relative humidity. At 30°C, less than 25 per cent of the adults were alive at the end of two weeks while 75 per cent of them were still alive at the end of five weeks at 20°C. Although the females lived longer at 20°C than at 25°C, they laid only a few eggs, remained quiescent m.ost of the time, and caused very little feeding injuries. At 2SoC in com.bination with 65 to 70 per cent relative hum.idity, the m.ajority of the fem.ales lived for over a m.onth, laid m.ore eggs than at other temperature and humidity com.binations, and oviposition continued daily up to a day prior to death.. For each respective decrease and increase in temperature below 20°C and above 30°C, longevity of the adults shortened at a 55. faster rate at the high than at the low tem.perature levels. At 3ZoC, none of the adults were alive after 7 days, whereas at lOoe som.e were still alive after 23 days. 56. 90 80 70 > I- :J j:!60 0:::o ~ 50 I- Z W 040 0::: W a.. 30 20 10 23456 7 8 9 WEEKS Figure 13. Longevity of the adults of Brevipalpus phoenicia (Geijskes) at the different temperatures in combination with 65 to 70 per cent relative humidity. 57. BIOLOGICAL OBSERVATIONS Molting B. phoenicia, like most other tetranychids, molts three times during its life cycle; at the end of the larval, protonymphal, and the deutonymphal stages. In the process of molting, the integument to be cast off splits transversely across the dorsum slightly in back of the humeral setae, along the lateral margins of the podosoma, and transversely across the venter at the level of the frontal margin of the anus. The emerging mite pushes itself backwards, frees the front two pairs of legs from inside the exoskeleton of the previous stage and, in doing so, the exuvia separates into t"w-v sections along the splits mentioned above. The small posterior section remains attached to the opisthosoma of the newly emerged mite until rubbed off and the large anterior section remains attached to the plant sur face for a long time and serves as a common site for oviposition. When the front legs are freed, they are used to withdraw the rest of the body from the exuvium. The molting process, from the appear ance of the split on the dorsum until the emergence of the mite from the exuvium required from 20 to 45 minutes at 250 C in combination with 65 to 70 per cent relative humidity. Feeding B. phoenicis is an active feeder, feeding at all hours of the day and night during the greater part of its active phases. Feeding is 58. especially intense and its resulting damage very extensive when tem perature is between 250 C to 300 C and relative humidity high. This species feeds on the stems of many kinds of plants; however, when high population density prevails, some individuals emigrate to other parts of the plant. On papaya plants, this mite usually feeds on the trunk at the l.,vel where the bottom whorl of leaves are attached. As intraspecific competition for food and space intensifies, the mites feed upwards on the trunk and outwards onto the leaf petioles and fruits, leaving a large conspicuous damaged area behind them. In feeding, the needlelike chelicerae are used to puncture the epidermal cells. The sap that oozes out from the wounded cells is mixed with saliva and imbibed into the digestive tract of the mite. The immediate area around the feeding puncture becomes raised and blisterlike as though caused by a toxic substance. Later, the affected tissue dries up, dies and becomes discolored. Since many feeding punctures occur close together, the affected areas coalesce to form a large continuous calluslike, tannish, scaly and/or scabby area (Fig. 14). The feeding damage is very pronounced when young papaya fruits are attacked for the affected areas become sunken due to the differential growth of the injured and uninjured tissues. The mites sometimes puncture the latex glands while feeding, causing a copious outflow of a milky white liquid which mars the appearance of the fruit (Fig. IS). All stages of the mite in the path of the flow of the 59. ":-. "";""', '.. Figure 14. Feeding injury caused by Brevipalpus phoenicis (Geijskes) on papaya fruit. 60. sticky latex are engulfed and drowned in it. The stem of papaya which normally remains green for a long time takes on a tan, suberized appearance prematurely and makes a spindly growth when heavily infested by B. phoenicis. A disease of orange known as Lepra explosiva in Argentina, originally thought to be caused by a fungus (Marchinatto, 1935) and later by a virus (Marchinatto, 1938; and Blanchard, 1939), is now attributed to toxins injected by ~. obovatus in the process of feeding (Carter, 1952). B. phoenicis has been collected from an orange tree exhibiting symptoms of Lepra explosiva in Paraguay (Nickel, 1958). In addition to the feeding injury described above on papaya, B. phoenicis causes pitting and splitting of the sld.n of orange fruits (Planes, 1954), scarring of tangerine fruits (Nickel, 1958), galling of sour-orange seedlings (Knorr, et al., 1960), and defoliation and vine dieback of passion fruit (Fig. 16). Mating Mating is seldom seen because 'of the scarcity of B. phoenicis males. During the two years of study, only six matings were ob served. In every case, the males mated with non-gravid females about a day old and remained in copula for about 15 minutes. In mating, the male approached the female from the posterior, rested his two pairs of front legs on the dorsum of the female's opisthosoma, 61. Figure 15. Feeding injury caused by Brevipalpus phoenicis (Geijskes) on papaya fruit. Note the exudates from feeding punctures. Figure 16. Feeding damage caused by Brevipalpus phoenicis (Geijskes) a on passion fruit. .N 63. and crawled beneath the opisthosoma so that one-half of his body was beneath hers. Simultaneous to crawling beneath the female, the opisthosoma of the male was bent upward and forward in a form of a ll Ile until the tip came in contact with the posterior end of the female's opisthosoma. Attached to the female in this position, the male walked along on his two hind pairs of legs, holding on to the dorsum of the female's opisthosoma with the front two pairs of legs and fol lowed her wherever she went. These mated females produced only female progenies as did the unmated females under laboratory con ditions so it was not possible to find out if the males were functional or otherwise. Cytological confirmation of this was unsuccessful for the standard method of chromosome determination using the squash technique with either aceto-orcein, aceto-carmine or Snow's stains failed to bring forth the chromosome complement of this species al though hundreds of eggs and adults were treated and examined. Sex Ratio As stated earlier, males have not been found in many parts of the world where this species is known to occur. Here in Hawaii, males comprised less than 1 per cent of the 6, 774 adults collected from various localities and at different seasons during 1962-63. There were no indications of seasonal or local abundance of males. In the laboratory, several generations of.!!.:. phoenicis were reared without males. No males were obtained from females of all ages 64" which were reared under the different temperature and humidity con ditions. Also, mated as well as unmated females produced only female progenies. These rearing data, plus the occurrence of pre.. ponderance of females in nature, indicate that parthenogenisis is the principal mode of reproduction in this species. Dispersion Man, in transporting plants from place to pl.ace, has unknowing.. ly disseminated B. phoenicis to many distant places. The ability of this mite to subsist on many different kinds of plants has certainly enhanced its rapid spread and establishment in many tropical areas of the world. Within a given area, birds, insects, mammals, wind, and rain have been incriminated as disseminating agents of many organisms. Of these, wind has been proven to be the most important agent of dispersal for many spider mites (FIeschner, .!:! al., 1956; and Boyle, 1957). Likewise in this study, wind was demonstrated as an impor.. tant disseminating agent of ~ phoenicis. Several microscope slides coated with "Tanglefoot" and strips of fly paper were placed at vary ing distances from a papaya plant heavily infested with B o phoenicis and other species of mites. After a 24..hour exposure periodp 123 adults of ~ phoenicis and several specimens of Tetranychus telarius (L.) were trapped on the microscope slides and strips of 65. fly paper placed directly downwind from the source of infestation. None was found on those placed upwind from the source of infestation. The slides and fly papers placed nearest to the source of infestation contained the greater number of mites. One individual was taken on a slide placed as far as 50 feet away from the infested papaya plant. Another common way in which wind may play an important part in mite disper sal is blowing fallen leaves with mites on them for great distances. Although B. phoenicis commonly feeds on the stems, crowded conditions cause many individuals to establish themselves on the petiole and on the lower surface of leaves along the main veins. Intensive feeding causes the leaves to drop prematurely and, when windy, these infested leaves are blown some distances away from the source plant. Should one of these leaves land fortuitously on or in the vicinity of a suitable host plant, an incipient mite population can be started by this means. Dispersion by migrating from plant to plant by crawling over non-plant surfaces is unlikely when great distances are involved for none of the active stages of B. phoenicis are able to live for more than three days without food. In closely set plants, however, disper sion by crawling f:rom plant to plant is possible for under conditions where plants were sheltered from wind and rain, clean plants became readily infested when placed near infested ones. Also, many mites were caught in the sticky bands that were wrapped around the bottom 66. of the tTunks of both infested. and uninfested papaya plants to study the migration of B. phoenicis. The bands on the uninfested plants were adjusted to trap immigrating mites and those on the infested for emi grating mites. Emigration of mites from the infested plants started when the plants became over-populated and suitable feeding areas scarce. Immigration onto uninfested plants occurred soon after emigration started; however, the number of immigrants was con siderably less than the emigrants. Apparently, many of them died in the process of finding a suitable host during migration. Plants in direct contact with the infested plants became infested much sooner than those somewhat removed from the source of infestation. The outward migration of mites due to population increase is very evident on passion fruit for the vines intertwine and form a contiguous mass of growth. On this plant, B. phoenicia foci of infestation enlarge concentrically, leaving in their wake a conspicuous feeding damage characterized by defoliation and vine dieback. 67. POPULATION STUDIES Seasonal Abundance The seasonal fluctuations of the ~ phoenicis population densi ties were studied over a two-year period at two localities, Manoa and Kaneohe, Oahu, Hawaii. Backyard papaya plants in their first year of fruiting and receiving no pesticidal treatment were used for follow ing the monthly fluctuations of the mite populations. The monthly samples consisted of 40 imprints made with adhesive tapes taken from 10 plants at each locality. Each imprint consisted of an area 6.25 square centimeters of the trunk. The imprints were taken from four sides of the trunk and between six to ten inches below the attacbm.ent of the bottom whorl of leaves for here is where the B. phoenicis populations are usually concentrated. All stages of ~ phoenicis were present at every sampling date throughout the two-year period but their numbers varied from month to month at the two localities. All stages of the mite were numerous from June to October and scarce from December to May, and were more abundant in 1962 than in 1963. The monthly densities and fluc tuations in the egg and adult populations which were very sim.ilar at the two localities during the two-year period are shown in Figure 17. The nUIIlber of individuals, especially the active mites, decreased suddenly following a heavy rain and increased gradually with the return of warm and hurm.d conditions. Rain not only ha:m.pered the 68. MANOA POPULAnON I 0"0 I I "'0 I : '0 o I\ I I \ ,I I \ 9 b I \ I , I 1963 KANEOHE 0"0"""I V'V'\ (/) R J' '\ ./EGG POPULATION ~200 I b-u \~ ::) o I \ () I 0 oI \\ \ \ q P, 0- \I',0 \'0,\~ " o b'O J F M AM JJ A SO N OJ F M A M J J A S 0 r'f 0 1962 ' 1963 Figure 17. Egg and adult densities and fluctuations of Brevipalpus phoenicis (Geijskes) populations during 1962 and 1963 at Manoa (upper) and Kaneohe (lower). Oahu, Hawaii. 69. movement of the active mites but washed off many of them from the plant surface; however, it had little effect on the eggs and the inactive mites which are more firmly attached to the plant surface. In areas and during periods of adverse climatic conditions, many of the mite s were observed feeding on the sheltered sides of sterns, leaves, and fruits away from direct exposure to sun, rain, and wind. The number of generations produced at Kaneohe and Manoa during 1962 and 1963 was impossible to determine because of the great overlap of the different generations caused by continuous reproduction throughout the year. However, based on the information obtained froIn the life history studies conducted in the laboratory, at least 10 generations per year were probably produced in the plots during the two-year period of study. Westation B. phoenicis infestations varied between the different kinds of plants, localities, and seasons. Infestations on papaya were found at all of the locations on Oahu from. sea level to about 1,000 feet elevation where this crop is grown extensively. Out of the 350 plants examined during 1963 at different months of the year, 253 of them were infested by B. phoenicis. All stages of the mite were present throughout the year at all of the localities. Older papaya plants of fruit-bearing age were more heavily infested than younger plants of 700 pre-fruiting age. One of the plants in its f~r st year of fruiting had 3,094 !!:. :phoenicis in all stages of developm.ent within an area of 6.25 square centimeters on the trunk surface, with lesser numbers on the leaf petioles and fruits. On the fruits, ~ phoenicis infesta- tions were usually concentrated on the side of the fruit that was in direct contact with the infested trunk or with another infested fruit. Those fruits located lower on the trunk were m.ore heavily infested than the younger fruits and blossom.s closer to the apex of the trunk. None of the other species of plants studied were as heavily in- fested by B. phoenicis as papaya. The highest num.ber of l!. phoeni- cis counted within an area of 6. 25 square centitneters of stem. - ' surface was 181 on passion fruit, 59 on lem.on, 50 on anthurium., 45 on hem.igraphis, and 8 on hibiscus. On other host plants listed in Table ill, large am.ounts of plant m.aterial had to be exam.ined before all stages of~ phoenicis were encountered. Infestations by this species of m.ite were not found on any of the above-mentioned host plants when found growing in areas above 2,500 feet elevation where rainfall is ~bundant and temperature drops below 200 C for many days out of the year. 71. NATURAL CONTROL FACTORS There are many factors or conditions, both biotic and abiotic, which influence the population density of B. phoenicis in a given area. Abundance of host plants, warm. and humid climate, and paucity of natural enemies are some conditions which favor high population density of this mite, whereas conditions contrary to these tend to depress it and favor the natural control of the pest. In Hawaii, B. phoenicis is very abundant in areas between sea level and 1, 000 feet, scarce between I, 000 and 2, 500 feet, and has never been recovered from areas above 2, 500 feet in elevation. Since host plants are abundant in all of the areas, this factor is not the cause of the differ ences in population density. However, the laboratory studies revealed that temperature does greatly affect the reproductive and survival potential, and this is probably the main factor which causes B. phoenicis to be of no econom.ic importance in areas above 1,000 feet elevation. Here, temperatures drop periodically to a level where mortality is considerably greater than natality and completion of a life cycle is not possible. Temperature conditions along the coastal areas in Hawaii are favorable for continuous reproduction throughout the year at nearly maximum reproductive and survival potential; howevers the popula.. tion density of B. phoenicis has never been observed in any locality to reach the point where food and space become limiting due to 72. intraspecific competition. Food and space do not become lim.iting over a whole orchard or locality but can become lim.iting on indivi dual plants due to both intra- and interspecific competition. Papaya, for example, is attacked by at least seven species of phytophagous mites other than the several species of insects which are of minor importance (Holdaway, 1941). The mites are: Tetranychus telarius (L.), Eutetranychus banksi (McGregor), Panonychus ~ (McGregor), Tuckerella pavoniform~s (Ewing), Tuckerella ornata (Tucker), Hemitarsonemus latus (Banks), and B. phoenicis. !. telarius, !:h latus, and B. phoenicis are the major pe sts of papaya. Individuals of these three species have been observed to coexist, increase to tremendous numbers, and to severely damage individual plants to the extent that the food media were no longer suitable for the members of their own species as well as those of the other species. Under such intense conditions of intra- and interspecific competition, many individuals of B. phoencis die from starvation and predation by ants, mites, spiders, and other predators which are fairly common in Hawaiian soils in the process of migration to other host plants, es pecially when great distances are involved. Even though some individuals of B. phoenicis are successful in reaching a host plant, it may be already occupied by some other organisms which compete with this species of mite for the same food and space, or the new host 73. plant may not be as conducive for population increase as papaya. The latter is evidenced by the considerably lower infestation indices of the mite on different kinds of plants mentioned earlier and by the lower fecundity data reported by authors who reared ~ phoenicis on plants other than papaya (Planes, 1954; Baptist and Ranaweere, 1955; Dosse, 1957; and Moutia, 1958). Within the favorable ranges of temperature and humidity, one of the most conspicuous natural factors that keeps B. phoenicis from reaching epidemic proportions is natural enemies. Murna (1958) noted a strong negative correlation between the summer-fall infestations of !h phoenicis and a complex of Typhlodromus and Arnblysiopsis on citrus in Florida. Although actual predation was not observed, he considered these phytoseiid mites to be the principal cause for the reduction in infestations of B. phoenicis which undergo cycles of high and low intensity in Florida. In Hawaii, at least four species of pre- dators, three mites and an insect, have been observed feeding on B. phoenicis. These are: Phytoseiulus macropilis (Banks) (Mesostigrnata: Phytoseiidae), Arnblyseius largoensis (Murna) (Mesostigmata: Phytoseiidae), Mexecheles hawaiiensis (Baker) (Prostigmata: Cheyletidae), and Sticholotis punetata Crotch (Coleop- tera: Coccinellidae). P. macropilis was first reported from Hawaii in 1953 bv - - . . Cunliffe and Baker while this is the fir st report of A. largoensis for 74. Hawaii. Besides Hawaii, the former species occurs in Florida, California, Canary Islands, Puerto Rico, and Panama (Cunliffe and Baker, 1953; and Chant, 1959), and the latter species in Florida, Guatemala, Mexico, and Japan (Chant, 1959; and Ehara, 1959). Both species of phytoseiids usually feed on spider mites, but when these preferred sources of food become scarce, they feed on other mites. Adults of P. m.acropilis and A. largoensis were seen on several occasions feeding on eggs of B. phoenicis on the petioles, fruits, and stems of papaya. After making contact with an egg, it took an adult of P. macropilis two minutes to pierce the chorion and withdraw the internal contents of the egg. Although P. macropilis and A. largo ensis feed on B. phoenicis eggs readily, there were no indications that they are able to live and reproduce exclusively on them, for eggs and larvae of these predators which occur commonly in association with spider mite populations were never found within the colonies of B. phoenicis. M. hawaiiensis was originally described from Hawaii based on specimens collected in 1941 from papaya fruits at Kailua, Oahu (Baker, 1949). Since then, this species has been collected on other kinds of plants infested by B. :phoenicis from the islands of Maui, Kauai, and Oahu. Also, this predatory mite has been reported from Florida recently (DeLeon, 1962; and Muma, 1964). The larvae, nymphs, and adults of M.hawaiiensis were seen feeding on all of the 75. active stages of B. phoeniCis, and all stages of this predator were found in close association with their prey. Individuals of M. hawaii ensis were seldom seen out in the open but were seen hiding in crevices, beneath leaves, between fruits, and in other protected places fr'om where they ambushed their prey. As a prey approached one of these hiding places, the predator dashed out, grabbed hold of one of the prey's appendages with its highly modified pedipalpi, and carried the victim back to its hiding place for feeding. A venomous substance was probably injected into the prey for it became paralyzed simultaneous to being captured by.M.• hawaiiensis. The chelicerae of the predator were inserted into one of the legs of the prey from where in less than 10 minutes the body contents were completely with drawn, leaving only the exoskeleton unconSUn1ed. The remains were carried and disposed outside the hiding place of the predator. The few numbers of carcasses of B. phoeniCis left accumulating around each hiding place suggest that M. hawaiiensis does not require much food for sustenance. Out of a total of the 535 predators found in close assoCiation with B. phoeniCis populations during 1962 and 1963, 467, or 87 per cent, of them, were M. hawaiiensis. ~ punetata, a tiny cocCinellid, was seen attacking ~ phoenicis for the first time in Hawaii in June, 1964. This predator was intro duced into Hawaii from China and Japan as early as 1894-95 to control scales ~Fullaway, 1920). ~ punctata was not seen preying on 76. B. phoenicis until this late date probably because of its nocturnal feeding habit. Some 30 adults were seen feeding on B. phoenicis in festing papaya plants on the University of Hawaii Campus, Honolulu, Hawaii, during four nights of observation. They appeared at dusk from within the ground litter at the bases of the papaya plants and climbed up the trunks to feed. When artifical light was directed on them, they stopped feeding and moved away from the lighted area. They finished feeding and left the plants before midnight. No indivi duals of §.. punctata were seen feeding on B. phoenicis during the day. The population density of B. phoenicis on these papaya plants dropped to a low level two weeks after §.. punctata adults were first seen in close association with the mites. This sudden reduction of the B. phoenicis population was undoubtedly caused by~ punctata for dissections of some of the adults caught before returning into the ground litter showed fragments of m.any individuals and all stages of ~ phoenicis in their digestive tracts. Enzootics or epizootics caused by pathogenic organisms, such as fungi, bacteria, and viruses, were not encountered in populations of B .. phoenicis.. However, two species of fungi, Hirsutella besseyi Fisher and H. thompsonii Fisher, were found infecting other species of phytophagous mites .. All of the above-mentioned predators have been observed to bring under control isolated populations of~. phoenicia; however, they are 77. inadequate as economic control agents because their predatory activity became apparent only when the prey population density was very high and severe plant damage had already been inflictedo There fore, in areas where economic control of B. phoenicia is needed, other control agents must be introduced. 78. Chemical Control In recent years, many chemicals with acaricidal properties have becom.e available but only a few of these can be used to control B. phoenicis on papaya because of various limitations and restrictions. Some of the pesticides which have been proven effective for the control of the comm.on species of spider mites (Family: Tetranychidae) have been shown to be ineffective against some species of false spider mites (Family: Tenuipalpidae) (Pritchard, 1949; Hamilton, 1953; and Morishita, 1954). Many more pesticides of the chlorinated hydrocarbon than organophosphor'ous derivatives have been reported to give excellent kill of false spider mites (Pritchard, 1949; Hamilton, 1953; and Morishita, 1954). Some of the pesticides toxic to the false spider mites cannot be used on certain kinds of plants because of their phytotoxic propensity. Papaya, a cornmon host of B. phoenicis, was found to be very susceptible to phytotoxic injuries when treated with most of the organic pesticides which were used for the control of mites on other crops prior to 1959 (Sherman and Tamashiro, 1959). Of the organo phosphorous pesticides, only Diazinon has been reported to give excellent kill of a species of false spider mites, B. obovatus (Mori shita, 1954), but it was found to be extremely phytotoxic to papaya. Malathion is innocuous to papaya but it proved to be ineffective against B. phoenicis. 79. Until recently, sulfur was the only pesticide known to be effec tive against B. phoenicis and also fairly safe to use on papaya from. the standpoint of phytotoxicity under m.o st of the clim.atic conditions which prevail in Hawaii. Since large am.ounts of sulfur, five to six pounds of 95 per cent wettable powder, are required to give good con.. trol of som.e of the mites infesting papaya, m.any of the growers are reluctant to apply this pesticide on fruit...bearing plants because it leaves unsightly deposits on the fruits. Furthermore, search for other acaricides becam.e necessary because many species of m.ites coexist on papaya and one of the most pestiferous of them, '!.. telarius, cannot be controlled effectively with sulfur (Sherman and Tam.ashiro, 1959). Those pesticides which have been reported to be fairly innocuous to papaya (Sherman and Tam.ashiro, 1959), and those which gave negli.. gible injuries to fruit-bearing plants in preliminary studies, were tested for their effectiveness against B. phoenicis. Of the pesticides in which both wettable powder and emulsifiable formulations are known, the former was selected because this form of most pesticides has been shown to be less phytotoxic to papaya than the corresponding emulsi fiable form (Sherman and Tam.ashiro, 1959). The performance results of the different pesticides used are shown in Tables VI, VII, and Vill. Karathane, Diazinon, and aram.ite gave good control of B .. phoenicis on other plants but were not used in this study for they were found to be very phytotoxic to papaya. 80. All concentrations of Kelthane, Pentac, and Morestan and certain of the higher concentrations of Chlorobenzilate, sulfur, and ovex gave good kill of !h. phoenicis adults (Table VI), but most of thero showed poor ovicidal properties (Table Vill). Morestan was the only pesticide which caused high mortality of both the adult and egg stages. Malathion, at all concentrations, caused no significant kill of B. phoenicis females, but the lower concentrations of this pesticide appeared to have induced oviposition in the treated feroales (Table VII). B. phoenicis adults died within 2.4 hours after applying lethal dosages of Kelthane and Chlorobenzilate, whereas those treated with lethal dosages of Pentac, Morestan, ovex, and sulfur died four to seven days after treatroent. Although the females Lived for several days after treatroent with these pesticides, they fed very little, laid only few eggs (Table Vil), and remained lethargic most of the tim.e. Adults treated with Kelthane and Chlorobenzilate died with their legs fully extended and their body posture posed like that of living indivi duals while feeding or when at rest so, until probed, the freshly killed individuals were difficult to distinguish from the living ones. Those killed by the other pesticides were readily distinguishable from the Living ones for they died with their front two pairs of legs retracted beneath the venter of the body. Many of the eggs that were deposited on the surfaces of the rn.edia just prior to and after exposure to treatroent with all concentrations of 81. Kelthane, Pentac, ovex, and sulfur, and with concentra.tions less than one pound active material of Chlorobenzilate per 100 gallons of water, hatched 10 to 12 days later and the resulting larvae fed and continued to develop on the treated media without showing ill effects from the residues. Apparently, these pesticides lost their toxic properties within 10 days under laboratory conditions. If this is true, they un doubtedly deteriorate to non-toxic levels much faster under field con ditions. When using one of these pesticides with poor ovicidal and seemingly short residual properties, a second application within two to three weeks after the first becomes necessary in order to control B. phoenicis effectively for it can escape control in the egg stage which has a fairly long incubation period. Although effective against B. phoenicis, some of the above mentioned pesticides and their concentrations should not be applied to fruit-bearing papaya plants because of phytotoxicity. Oozing of latex from the epidermis of green fruits in areas where large amounts of pesticideg had accumulated were noticed soon after applying ovex at two pounds, Chlorobenzilate at one and two pounds, and Pentac at two pounds of active material per 100 gallons of water under field conditions. These areas of latex exudations developed into scars of various sizes and shapes in about three weeks after the pestkide application which greatly marred the appearance of the fruits 82• .Figure !8~ L1'ljury caus.ed by Ghlol"'obenzilate at 1 pound of active material per 100 gallons of water" 83. Figure 19. Injury caused by Pentac at Z pounds active material per 100 gallong of water. 84. Figure 20. Injury caused by ovex at 2 pounds active material per 100 ga.llons of wa.terg 85. (Figs. 18, 19, and 20). Kelthane and Morestan were found to be innocuous to papaya fruits at concentrations as high as two pounds of active material per 100 gallons of water, but they are not recom mended for use at these high dosages for not only is it uneconomical but the unsightly depo sits on the frui~s mentioned earlier would be a problem. Kelthane, Morestan, Chlorobenzilate, Pentae, and ovex are not to be used on papaya grown for the commercial market as they have not yet been cleared for use on this crop. Sulfur and Volck Oil Supreme are the only two pesticides which are toxic to some of the stages of B. phoenicis and can be used on papaya for they are exempt from the requirement of a tolerance. Whereas most petroleum oils and even er.L.ulsifiable forms of many pesticides are known to be phyto toxic to papaya, Volck Oil Supreme, a highly refined petroleum oil, caused no obvious phytotoxic injury to fruit-bearing papaya plants. TABLE VI. PERFORMANCE OF DIFFERENT. PESTICIDES AGAINST THE ADULTS OF BREVIPALPUS PHOENICIS (GEIJSKES) Pounds active material per Pesticides 100 gallons Formulations No. Alive a/ Statistical significance b/ Malathion 1/4 25% WP 5.10 Ovex 1/4 50% WP 5.05 Check 5.02 Malathion 1/2 250/0 WP 5.02 Malathion 1 25% WP 4.90 Malathion 2 25%WP 4.70 Ovex 1/2 50% WP 4.48 --'I Chlorobenzilate 1/4 25%WP 3.92 ] Volck Supreme 3 EC 3.25 :::J Volck Supreme 2 EC 2.55 Volck Supreme 6 EC 2.38 Volck Supreme 4 EC 2.15 Ovex 1 500/0WP 2.10 J] Sulfur 3 95% WP 1. 90 Chlorobenzilate 1 25% WP 1.45 Sulfur 4 95% WP 1.40 ] Pentac 1/4 50% WP 1.35 Chlorobenzilate 1/2 25% WP 1.25 l 0:> •0' TABLE VI. Con.tinued Pounds active material per Pesticides 100 gallons Formulations No. Alive eJ Statistical Significance "'e.l Morestan 1/4 250/0 WP 1.20 Morestan 1/2 25%WP 1.10 Morestan 1 25% WP 1.00 Morestan 2 25%WP 1.00 Chlorobenzilate 2 25%WP 1.00 Ovex 2 50%WP 1.00 Sulfur 5 95% WP 1.00 Sulfur 6 95%WP 1.00 Pentac 1/2 50%WP 1.00 Pentac 1 50% WP 1.00 Pentac 2 50%WP 1.00 Kelthane 1/4 25%WP 1.00 Kelthane 1/2 Z5%WP 1.00 Kelthane 1 25% WP 1.00 Kelthane 2 25%WP 1.00 a/ N III 25. Average of four replications. The data were transformed according to the formula .jXfT. b/ At 5 per cent level, according to multiple range test of Duncan (1955). WP =. Wettable powder EC a Emulsifiable concentrate 00 .-.] TABLE VII. NUMBER OF EGGS OF BREVIPALPUS PHOENICIS (GEIJSKES) COUNTED ON TREATED SURFACE ONE WEEK AFTER .APPLICATION OF THE DIFFERENT PESTICIDESo PoUnds active material per Pesticides 100 gallons Formulations No. of eggs a/ Statistical significance b / Malathion 1/2 250/0 WP 194.75 ::J Malathion 1/4 250/0 WP 138.75 Malathion 1 250/0 WP 129.75 Check 128.50 Ovex 1/2 500/0 WP 116.25 Malathion 2 250/0 WP 110.75 Ovex 1/4 500/0 WP 105.50 Valek Supre:rne 3 EC 68.50 =:1 Chlorobenzilate 1/4 250/0 WP 32.50 Volck Supreme 6 EC 20.75 Ovex 1 500/0 WP 20.50 Volek Supreme 2 EC 19.25 Sulfur 3 950/0 WP 19.25 Pentac 1/4 500/0 WP 16.50 Pentac 1/2 500/0 WP 16.25 Ovex Z 500/0 WP 13.75 Sulfur 4 950/0 WP 13.50 Sulfur 5 950/0 WP 12.75 0:> •0:> TABLE VII., Continued Pounds active material per Pesticides 100 gallons Formulations No. of eggs al Statistical significance bl Volck Supreme 4 EC 11.75 Morestan 1/4 25%WP 11.25 Sulfur 6 95% WP 10.75 Pentac 1 50%WP 10.75 Kelthane 1/2 25%WP 10.50 Pentac 2 500/0 WP 10.00 Morestan 1 250;0 WP 9.75 Morestan 2 25%WP 9.50 Morestan 1/2 25%WP 8.50 Kelthane 1 25%WP 7.75 Kelthane 1/4 25%WP 7.50 Chlorobenzilate 1/2 25%WP 7.50 Chlorobenzilate 1 250;0 WP 7.50 Chlorobenzilate 2 25%WP 7.50 Kelthane 2 25% WP 6.50 ;;j Average of four replications. Pre-treatment N = 25 females. Eggs laid prior to death or during first week afj;er treatment. r:J At 5 per cent level, according to multiple rang~: test of Duncan (1955). Wettable powder 00 WP = --D EC = Emulsifiable concentrate . 1'ABLE Vill.. OVICIDAL EFFECT OF DIFFERENT PESTICIDES ON THE EGGS OF BREVIPALPUS PHOENICIS (GEIJSKES). Pounds active material per Per cent of Pesticides 100 gallons Formulations eggs hatched al Statistical. significance b/ Check 87.0 Malathion 2 25% WP 84.0 ] Sulfur 6 95% WP 80.5 Keltha.ne 2 25% WP 69.5 Ovex 2 50% WP 68.0 Pentac 2 50%WP 67.5 ] Chlorobenzilate 2 25% WP 55.5 :::J Volck Supreme 6 EC 14.0 ::J Morestan 1/4 25% WP 2.5 Morestan 2 25% WP 1.5 ] a/ Average of eight replications. N· 25 eggs per replication.. bl At 5 per cent level, according to multiple range test of Duncan (1955). WP = Wettable powder formulation EC ~ Emulsifiable concentrate -.0 .o 91. DISCUSSION Studies on the biology of B. phoenicis have revealed that this species has many attributes in common with the other well-known false spider mites, 1b obovatus andlh californicus. Like them, B. phoenicis is polyphagous, reproduces mainly by parthenogenesis, males are very scarce, life cycle is fairly long, and it is tolerant of ._-,-- . certain of the organophosphorous pesticides. Despite these similari- ties, B. phoenicis possesses certain attributes which seem to be dis- tinctive for the species. The most striking attribute is its ability to thrive only within fairly narrow temperature range, while B. obovatus and !h californicus reproduce freely within a wider temperature range, 20°C and 30o C, with very little mortality occurring during the developmental stadia under laboratory conditions (Manglitz and Cory, 1953; and Morishita, 1954). The distributional patterns of these false spider mites in nature are in line with the laboratory findings. Here in Hawaii, B. phoenicis is very abundant only along the coastal areas to about 1,000 feet elevation where the temperature is fairly uniform throughout the year and does not deviate too greatly from 2.50 C for any length of tim.e, whereas the other two false spider mites are more widely distributed from sea level to about 3,500 feet elevation where the ten'lperature conditions at the higher elevations are m.ore variable and often drops below 2.0 oC for extended durations (Ripperton and Hosaka, 1942.). Also, both B. obovatus and B. californicus have been 92, reported from more countries outside the tropics tha,n B. phoenicis (Pritchard and Baker, 1958). Another distinguishing attribute of B. phoenicis is its feeding preference on the stems of plants. The foci of B. phoenicis infesta- tions are usually located on the stems while those of B. obovatus and ~. californicus are invariably located on the lower surfaces of leaves. These mites move away from their preferred feeding sites to other parts of the plant only when overcrowded conditions prevail. Although, the life cycles of the three false spider mites were carried out under slightly different laboratory conditions by the vari- ous workers (Manglitz and Cory, 1953; and Morishita, 1954), all indications are that the life cycle of B. phoenicis is definitely longer than those of B. obovatus and B. californicus. B. phoenicis com- pleted its development from the egg to the adult stage in 18.6 f:. 0.5 days at 30oC, 29.3 I:. 0.4 days at 250 C, and 48.9 /:. 1.5 days at 20o C. At the sam.e respective temperatures, the average developmental periods of B. obovatus were reported as 16.4, 28.0, and 42.0 days by Morishita (1954)0 Dosse (1959) found that B. phoenicis required about two days longer than~ obovatus to complete its development on ivy leaves at 24oC. Of the three species of false spider mites, B. californicus seems to have the shortest life cycle for }/ianglitz and Cory (1953) were able to rear this mite from egg to the adult stage in 26.2 days under temperature conditions ranging between 17. 90 C and 23. 9°C. Whereas the developmental rate of false spider mites is much faster at temperatures above 250 C than below it, the life cycle of B. califomicus is two to three days shorter at temperatures below 250 C than those of B. obovatus and B. phoenicis at 250 C. The developm.ental rate of the above three specie s of false spider mites is slow in comparison to that of som.e of the spider m.ites. Tetranychus desertorurn Banks and T. telarius (L.) are known to develop from. eggs to adults in just 6.90 t. 0 .. 5 days and 7.09 t 0.17 days, respectively, at 300 C (Nickel, 1960), while the false spider mites, B. phoenicis and B. obovatus, require on an average of at least 18.6 and 16.4 days, respectively, at the same temperature conditions. The conditions under which developm.ent is m.ost rapid is not necessarily favorable for population increase since m.ortality during the im.m.ature stage s can be much greater than natality as was shown in this study. Therefore, when optimum. survi val conditions are taken into consideration, the developmental period of B. phoenicis is about four times longer than those figures shown above for the spider m.ites. The fecundity of both ~ phoenicis and B. obovatus is less than that of som.e spider mites. Tetranychus atlanticus McGregor, T. telarius, and T. desertorum females are capable of laying as many as 230, 194, and 187 eggs per individual, respectively (Cagle, 1949 and 1956; and Nickel, 1960); however, the maximum laid by any 94 .. species of false spider mite female is only 76 eggs. This low fecundity and the long developmental period of the false spider mite s are probably the main reasons why they are only occasional pests of perennial plants and are not as serious pests of agricultural crops as the spider mites. In Ceylon, B. phoe~ is reported to require about three year s to reach economi c proportions on tea plants which are pruned (Baptist and Ranaweera, 1955). Here in Hawaii, B. phoenicis normally requires about a year to build up to densitie s high . enough to cause noticeable damage to papaya. Since B. phoenicis reproduces mainly by parthenogenesis, it seems reaso:n.able to assume that the genetic composition of a popu- lation of this mite within an area is fairly uniform. Resistance to pesticides is less likely to be selected out from such a population because the gene pool is more limited than that of sexually reproduc ing species as the spider mites. This is probably the mai.Tt reason why resistance to acaricides which were once proven effective has not been reported for the false spider mites, whereas resistance to pesticides is a notorious and serious problem in the case of spider mites (Jeppson, 1961)0 However, the frequency of application of selection pressure such as a pesticide should be taken into consider ation. Since the false spider mites are only occasional pests of agricultural crops, none of the acaricides have been used extensive ly for their control as for spider mites and this also may be a reason 95. why resistant populations have not yet been selected out. Although. chemical control is the most effective means of sup pressing outbreaks of B. phoenicis, :many problems can arise in the atte:mpts to control this mite with che:micals. When chernical control is needed on a food crop, one :must rnake certain that the pesticide selected for application is approved and recom.:mended for usage on the particular crop and is used in strict accordance with the directions stipulated on the labels of the pesticide containers. On certain crops, only a few pesticides are cleared for use and these registered pesti cides may not be toxic to B. phoenicis even though they have been shown to be effective against other closely related species or they may be toxic to only certain stages of B. phoenicis. Here in Hawaii, when using pesticides which kill only certain stages of the mite, several applications within relatively short intervals are necessary for all stages of ~ phoenicia are present simultaneously the year around and the duration of certain of the stages is longer than the residual life of rnost pesticides. Cornbinations of pesticides, one that kills the egg with another that kills the active stages, seem like a ready solution to the problem of necessity of several and/or separate applications, but other problerns can arise in doing so. Sorne pesticides are innocuous to plants and very effective against certain stages of B. phoenicis when applied singly, but when co:mbined they :may becorne either phytotoxic due to synergism or rnay become ineffective against 96. the rnites. Furthennore, not all pesticides are cornpatible with each other. Some pesticides are very effective against B. phoenicis but they cannot be used because certain of the host plants of this mite are very susceptible to chemical injury. The reader is referred to the papers by Gast and Early P956) and Sherman and Tamashiro (.1959), and to the textbooks by Bailey and Smith (1951), Brown (1951), and Shepard (1951) for concepts on the phytotoxic properties of pesticides.. 97. SUMMARY The red and black flat mite, Brevipalpus phoenicis (Geij skes), is widely distributed throughout the tropical areas of the world. In Hawaii, this mite is very abundant on all of the major islands along the coastal areas up to about 1,000 feet elevation. The climatic conditions in these areas are favorable for continuous reproduction of B. phoenicis throughout the year. B. phoenicis inhabits and feeds on approximately 100 different kinds of plants. It is a major pest of perennial plants such as papaya, pas-sion fruit, tea, citrus, and several species of ornamentals. It usually feeds on the sterns of plants, but when food and space become limiting due to overcrowded conditions, some individuals move to other parts of the plant and form. colonies. Morphologically, B. phoenicis is a variable species. For this reason, several synonyms have been created. The most variable structures are the dorsolateral hysterosomal setae I and II, and the dorsocentral hysterosomal setae III of the larvae and nymphs. The Be vary from a tiny~ serrate setae to a large, broadly lanceolate, serrate setae. The larva, protonyrnph, and deutonyrnph of B o phoenicis are ve:r:-y similar to those of ~o obovatus Donnadieu» but the adults are readily distinguished from the latter specieso B o phoenicis is the only species known to have two pairs of sensory rods on tarsus II and five pairs of dorsolateral hysterosomal setae in the adult stage. 98. The life cycle of B. phoenicis is greatly influenced by tempera ture and hum.icIity conditions. The larva, protonymph, and deuto nymph spend about one-half of their stadia as active individuals and the remainder of the time as inactive individuals. Feeding, growth, and limited dispersion are accomplished during the active phase and ecdysis occurs during the inactive phase. The average durations of the different stages range from. 8.2 1:. 0.4 days at 300 e to 22.6 I:. 1.1 days at 200 e in the egg stage, 3.6 1:. 0.2 days at 30°C to 10.5 t. 0.7 days at 200 e in the larval stage, 3.1 I:. 0.4 days at 300 e to 8.2 t 0.7 days at 200 e in the protonymphal stage, and 3.7 t 0.5 days at 300 e to 7.5 f:. 0.9 days at 200 e in the deutonymphal stage. At 250 e and 65 to 70 per cent relative humidity, conditions most favorable for survi val and population increase, B. phoenicis completes development from the egg to the adult stage in 29.3 f:. 0.4 days. Development is much faster at temperatures above 250 e than below it; however, mortality of the im.m.ature stages increases with deviation of tempera ture away from 250 e until completion of the life cycle is no longer possible at temperatures above 300 e and below 20oe. All stages of the mite are able to withstand brief exposures to temperatures below 200 e better than temperatures above 30oe. The B. phoenicis adult population is predominantly female. Males have been reported as non-existent in many parts of the world, but here in Hawaii they make up about 1 per cent of the adult population. 99. Since umnated females are able to give rise to exclusively female progenies and males are very scarce, reproduction of the species is mainly by parthenogenesis. At 250 C and 65 to 70 per cent relative humidity, B. phoenicis females start to oviposit in 3.5 1:. 0.9 days after emergence and lay from one to four eggs per day for a total of 57.5 1:. 7.4 eggs per female during their life span of 34.8 1:. 4.5 days. Preoviposition period is longer at 300 C than at 250 C or 20o C. Females live longer but lay only one-fifth as many eggs at 200 C than at 250 C. Four species of predators; Phytoseiulus macropilis (Banks), Amblyseius largoensis (Muma), Mexecheles hawaiiensis (.Baker), and Sticholotis punctata Crotch, feed on certain stages of B. phoenicis in Hawaii. Of these, M. hawaiiensis is the predominant predator. All of the active stages of this cheyletid mite feed on the active stages of B. phoenicis. These natural enemies control isolated populations of ~ phoenicis, but are often inadequate as economic control agents. Chemical control measures can be used to effectively depress outbreaks of B. phoenicis. Morestan is toxic to all stages of the mite, whereas Chlorobenzilate, Pentac, Kelthane, and sulfur give excellent kill of the active stages only. Volck Supreme, a highly re fined petroleum oil, gives good kill of the eggs of B. phoenicis but only poor to fair kill of the adults. These pesticides are relatively non-phytotoxic to papaya, a plant that is very susceptible to chemical 100. injury, at the m.inim.um dosage of effectiveness to B. phoenicia. Sulfur and Volck Oil Supreme are the only two pesticides which can be used to control &. phoenicis on papaya grown for the com.m.ercial m.arket, while the other above-m.entioned pesticides are not yet registered for use on this crop. All stages of B. phoenicis are tolerant of m.alathion, an organophosphorous pesticide which is approved for usage on papaya and claimed to kill certain species of spider m.ites. 101. REFERENCES CITED Attiah., H. H. 1956. The genus Brevipalpus in Egypt. Soc. Ent. dlEgypte Bull. 40: 433-448. Bailey, S.. F. and L. M. Smith. 1951. Handbook of agricultural pest control. 191 pp. Industry Publications, Inc., N. Y. Baker, E. W. 1945. Mites of the genus Tenuipalpus (Acarina: Trichadenidae). Proc. Ent. Soc. Wash. 47(2): 33-38. __--:~_':""'. 1949. The genus Brevipalpus (Acarina: Pseudoleptidae). Amer. Midi. Na.t. 42(2): 350-402• .and A. E. Pritchard. 1960. The tetranychoid ------mites of Africa. Hilgardia 29(11): 455-574. Baptist, B. A. and D. J. W. Ranaweera. 1955. 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