TECHNICAL BULLETIN No. 54 JANUARY 1963

Zoogeographical and Ecological

Studies of Docus cucurbitoe(Diptera-Tephritidae) in India

JOSHIYUKI NISHIDA

HAWAll AGRICULTURAL EXPERIMENT STATION, UNIVERSITY OF HAWAll

CONTENTS

A CKNOWLED GME NT

I NTHODUCTION

M ETHODS

Field Methods

Laboratory Methods

ZOOGEO GHAPHICAL CONSIDEnATIONS

Distribution .

Original Home

E COLOGICAL CONSID EHA'rroxs

Physical Environment and Activity

Overwintering Behavior

Fecundity in Summer and Winter

Habitat and Host Relations

Natur al Enemies .

DISCUSSION

SUMMAHY

R EF EHENCES

P AGE

2

3

4

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5

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ACKNOWLEDGMENT

The studies reported herein were made possible because of the gen­erous financial and other forms of assistance that I received. It is withgreat pleasure that I express my thanks to th e United States EducationFoundation for its generous financia l support. Special thanks arc due Dr.Olive Reddick, Director, United States Educational Foundation in India,for her encour ageme nt and assistance in many ways. I am deeply indebtedto various members of th e Government Agricultura l Coll ege, Kanpur, whowere extremely helpful: Dr. R. K. Tandon, Dr. U. S. Sharga , Dr. A. S.Srivastava, Dr. N. S. Agrawal, and Mr. R. B. Mathur. I also wish to extendmy thanks to all Indian en tomologists and botanists for th eir va luableadvice and suggestions. I am indebted , also, to Dr. D. Elmo Hardy, Uni­versity of Hawaii , and to Dr. R. N. Mathur, Forest Research Institute,Dehra Dun, India, for their prompt identification of specimens sent to th em.

THE AUTHOR

D n. TOSHIYUKI NISHIDA is Associate Entomologis t at the H awaii AgriculturalExperime nt Station and Associate Professor of Entomology, University ofH awaii.

Zoogeographical and Ecological

Studies of

Dacus cucurbitae (Diptera-Tephritidae)

in India

TOSHIYUKI NISHIDA

INTRODUCTION

In 1899, CoquiIlett described a new spe cies of tephritid fly, Dacus cucur­bitae, from specim ens reared from cucurbits in Hawaii (Coquillett, 1899).Short ly th ereafter , the occurrence of this tephritid fly,' commonly knownas th e melon fly, was rep orted from India and from oth er countries. During1959-60, the writer had th e opportunity of studyin g thi s fly at th e Govern­ment Agri cultural College, Kanpur, Utt ar Pradesh , India. This paperpresents some of the zoogeographical and ecological studies conducted inIndia.

The study area include d most of India, an extensive country lyin g be­tween 7° and 37° North latitude. The distance between its south and northextremities is approximately 2,200 miles, and between its east and westextremi ties, about 1,200 miles. Geographe rs divid e th e Indian subcontinentinto three region s, the Him alayas, the Indo-Gangeti c Plains, and th e Dec­can Plateau. The mountainous Himalayan region lies at the nor thernextremity . Here are th e sourc es of th e Ganges, Indus, and Brahmaputrarivers. To the south of the Himalayas lie th e fertile Indo-Gangeti c Plain sthrough whi ch flow th ese three largest rivers of India. The tri angular,peninsular portion of south India is referred to as th e D eccan Plateau, whichis bord ered on the west by mountain ranges called th e W estern Ghats andon th e cast, by th e Eastern Gha ts.

The climate of India is diverse in many respects . There is, however , acertain climatic pattern common to many parts of th e country b ecause ofth e widespread influence of the monsoon. January to June is th e season ofthe northeast mon soon and during th is tim e th e preva iling northeast windsblow from th e inland regions of central Asia. During this period, th e temp­erature is low and the rainfall is scant. From March to June, th e tempera­tur e rises ra pidly, but th e ra infall con tinues to be scant. From June toDecember is th e season of th e southwest monsoon and, during thi s period,the winds shift to th e southwest. The period of high rainfall and hightemperature comes between June and September. From September toD ecember, th e temperature drops and the rainfall decreases.

4 HAWAII AGlUCULTUR AL EXP EHIMENT STATIO N

Although India is, in many resp ects, becaus e of its diverse terrain andclimate, an ideal locality for th e study of the ecology of D. cucurbitae,th ere is relatively little published literature on the melon fly in that country.This situation exists becau se of the greater economic importance of th isinsect in countries other than India. Amon g the important Indian publi­cations are thos e of Srivastava (1948) , Shah , Batra, and Rcnjhen ( 1948 ),Renjh en (1949) , and Batra (1953). In addition to these, th ere are shortnotes in such publications as Proceedings of th e Entomological Meetings ,Pusa, Pro ceedings of the Indian Academy of Science; Indian Mus eum Notes;Indian Journal of Agricultural Science; In dian Mu seum Notes; and report sof the dep artments of agriculture of various Indian states.

The life history of D. cucurbitae has been studied in Hawaii (B ack andPemberton, 1914, 1917, 1918) , in Formosa ( Kore ishi, 1937 ), in th e Philip­pines (Ponce, 1937) , and in India (Srivastava, 1948). Except for a gener­alized life cycle, no attempt will be made to give an extensive review ofthis subject, becaus e it has been ade quately covered by Christenson andFoote (1960) . Th e flies lay their eggs in the tissu es of the host plants . Afterth e eggs hatch, the larvae feed and bore into the plant tissues. When fullygrown, th e larvae pupate in th e soil. Th e adults, which emerge from pu­paria in th e soil, bore th eir way up out of the soil. These newly emergedadults fly onto favorable nonhost plants and here feeding and mating occur .Wh en gravid, the females move into areas wh ere host plants are pr esentand here th ey lay th eir egg s ( Nishida and Bess, 1957 ).

METHODSTh e results of these studies are based on field and laboratory observa­

tion s. Fi eld observations were made using th e Department of Entomologyand Zoology, Government Agricultural Coll ege, Kanpur, as headquarters .Laboratory studies were also conducted at th e same institution, using itsfaciliti es. Although not always feasible, efforts were made to utilize mate­rials available in India.

Upon my arrival in India, it was hoped that most of the investigationscould be carried out in the vicinity of Kanpur. Preliminary observations,however , showed that it was desirable to include all of India as the studyarea , since it was found that D. cucurbiiae was widely distributed throughoutthat country.

Field Methods

Situated in th e heart of the Indo-Gangetic Plains of North India, muchof the vast land surrounding my headquarters was agricultural land withvillages of various sizes scattered throughout. Fi eld trips were tak en atleast onc e a week to collect infested fruits and to make observations onth e activity and behavior of D. cucurbitae. In addition to these frequentshort trips, others of longer duration were taken to as many places aspossible in ord er to obtain distributional data and to correlate activity withvarious features of the environment.

DACUS CUCURBITAE IN INDIA 5

To obtain information on parasites and host plants of D . cucurbitae,field collections of fruits showing evide nce of infestation were made. Thesefruits were brought to th e laboratory in pol yethylene bags containing saw­dust, which absorbed th e excess liquid from the decaying fruit. Further­mor e, the sawdust was useful because, on long excursions, th e ma ggotspupated in it , and the pupae were sifted out afte r reaching th e labora tory.In th e laboratory th e inf est ed fruits were pl aced in gallon-size jars withsand from th e Ganges Hiver at the bottom. Upon pupation, th e pupae wereseparated from th e sand and placed in 8-dram shell vials. Upon emergence,th e number of adult fruit flies and th e number of parasites were recorded.

Th e climatological records were obtained from Sawyer and Reicheld er­fer (1951 ) , Strauss and Reichelderfer ( 1959), Kendrew (1953 ) , and th eGov ernment Agricultural Coll ege, Kanpur, India.

Laboratory Methods

The adults in captivity were kept in gallon-size glass jars that areavailable in Indian markets at a very reasonable price. Although not veryuniform in size, th ese handmade jars were suitable as small cag es. Thejars were placed in a hori zontal position on a table, and th e jar openingswere covered with thin organdy held in place with rubber bands that hadbeen made by cutting strips from th e inn er tubes of bi cycle tir es. Waterwas supplied by means of small earthen cups into whi ch was placed apiece of absorbent cotton, which wa s kept always moist by adding waterdaily. The food, whi ch wa s placed on a sheet of wax paper , consisted ofcan e sugar and yeast hydrolysate, a food supplement necessary for eggproduction ( Hagen and F inn ey, 1950 ).

The method for obtaining eggs from th e flies kept in captivity wassimilar to the one used by Keck ( 1951) . Small, circular or oval sectionsapproximately 2 inches in diameter were cu t out of fruits. The inn er softtissues were scraped off with a kitchen teaspoon , th e peripheral edges ofwhich had been ground into a cutt ing edge. The rind wa s then placed ona 2%-inch-square gla ss plate with th e convex inn er portion of th e rinddown against th e glass plate. To hold th e rind in place, melted paraffinwa s placed alon g the edge. Punctures were made in th e rind using a No.3 insect pin. Preliminary tests showed that th e rind of various cucurbitfruits, such as lauki, Lagenaria vulgaris Scr. ; kundru, Co ccinia indica W .and A.; ghia torai , Luffa aegUJ!!iaca Mill. ; arro torai , L acutangula Roxb.,and parwal, Trichosantlies diocia Hoxb. , were found satisfactory. Th e rindof Iauki was uscd most frequently because of its availability even duringthc winter months.

After exposing th e prepared rind to th e adults, eggs were laid , andth ese were th en brushed off from th e inn er surface of th e rind. The eggswere placed on black moist paper in petri dishes, and upon hatching, th eyoung larvae were transferred into th e rearing medium.

6 HAWAII AGRICULTURAL EXPERIMENT STATION

The rearing of larvae presented a difficulty because of the lack of re­frigeration facilities for storing th e media. A series of tests was conductedin an effort to rear th e larvae in media that did not require fresh fruits.Because of the availability of a large variety of dri ed legumes and otherseeds in India, tests were made to de termine wh ether these materi als couldbe utilized as rearing media. Ground dri ed seeds , of Cucumis sp.: grams,Phaseolus spp. ; and pulses, Vicia spp., Pisum sp., and Caianus indi cusSpreng, were tried. Although it was possibl e to rear larvae in these media,th e mortality rate was ver y high , apparently du e to rapid fermentation ofthe paste made with the dri ed seeds. Thus, all larva rearing was carriedou t usin g coarsely grated fresh lauki fruit, even though it was not alwaysconvenient to purchase fresh fruits whenever they were need ed. Pant, Gh ai,and Chawla (1959) have reported on an unfortified rice medium for therearing of D . cucurblta e. However, thi s medium was not tri ed, becauseth e publication did not appear until about th e time of my dep arture fromIndia.

The containers used in rearing the larvae were small, ear then, hand­made cups approximately 2% inches in diameter and 2 inches deep. Theywere placed in wide-mouthed glass jars which contained a layer of GangesRiver sand on the bottom. When larval development was completed , thepupae were collected and placed in 8-dram shell vials containing sand.Upon emergence, the adults were transferred into th e gallon-size glass jars.

ZOOGEOGRAPHICAL CONSIDERATIONS

It is more than 60 years since D. cucurbitae, the melon fly, was firstdescribed by Coquillett (1899). During thi s period, a considerable amountof information has appeared in various periodicals. This inform ation hasbeen extremely valuable in determining distributional patterns and in elu­cidating some of our ideas on this fly's origin.

DistributionThe presently known world distribution of D. cucurbiiae, as shown in

figure 1, reveals that its distribution is not extensive. This world distribu­tion includes India, Burma, Malaya, the Philippines, southern China, For­mosa, Okinawa and nearby islands, Kenya, Mauritius, Saipan, Guam, andHawaii. This pattern clearly indicates that D. cucurbitae is a componentof the fauna of the Oriental Region.

Figure 1 also indicates that the distribution of D. cucurbitae is restrictedto the area lying between 35° North latitude and 22° South latitude. Sucha distribution pattern shows also that this insect is adapted to tropical,subtropical, and, to a certain extent, temperate conditions.

The roughly elliptical shape of the distribution pattern shown in figure1 is of interest from an ecological viewpoint. If dispersal occurs at randomin a uniform environment, the pattern of distribution will be circular.However, this tendency is usually altered due to climatic differences along

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8 HAWAII AGRICULTURAL EXI'ERI:MENT ST ATION

the peripheral ar ea . Because climatic changes are of greater magnitudelatitudinally than longitudinally, th e pattern of distribution tends to assumean oval or elliptical shape. This tendency is clearly indicated in the distri­bution of D. cucurbiiae.

The northern and southern dispersal of D. cucurbltae ha s been hinderedby certain ecological barriers. From the ellip tical distribution pattern , itis evide nt that th e barrier to northward or southward dispersal is associatedwith climatic factors. Studies on the cffects of temperature on the variouslife stages of this insect indicate that low temperature is one of th e im­portant barriers to northward and SOli thward dispersal (Koidsumi , 1931,1933: Messenger and Flitters, 1954, 1958 ).

There ar e, without doubt, temporary establishments of D. cucurbitaeoccurring along the northern and southern peripheral ar eas. Hill (1915 )reported that the melon fly was collected in northern Australia, but it has notbeen found in Australia since that report. According to Back and Pember­ton (1917), this fly was rear ed by Compere from fruits collected in Naga­saki , Japan; but it appears that the fly has not becom e established in Japan,for Shiraki (1933 ) does not list it in his work on th e Trypetidae of theJapanese Empire. Temporary establishment has also OCCUlTed at least oncein California (Maehl er , 1957 ).

Original HomeThe original hom e of D. cucurbitae has long been a subj ect of specu­

lation, for it was recognized early that even though this insect was firstdescribed from specimens collected in Hawaii, Hawaii was not its nativehom e. In 1902, Perkins speculated that th e origin al hom e of this insect waseithe r Japan or China. According to Froggatt ( 1909), Bezzi (1913 ), andIllingworth (1913) , its native hom e was India. Severin et al. ( 1914) statedthat Compere was of th e opinion that D. cucurbitac was native to th ePhilippines. The Indo-Malayan region was also mentioned as a possiblelocality by Back and Pemberton (1918) . On the assumption that th edistribution pattern s have not changed in the past, th e original hom e mu stlie somewhere within the limits of the present distribution. The problem isto pinpoint the most likely areas on th e basis of available evidence. Anatt emp t will be mad e to present evide nce whi ch indicates that south Indiais the native hom e of thi s insect . Thi s evidence is based on host plantspecifi city and parasite complex.

The close affinity of D. cucurbitae to its host plants in the family Cu­curbitaceae is well known throughou t its distribution. Such close affinityindicat es that thi s insect is native to areas where th e Cuc urbitaceae haveoriginated . Accor ding to Vavilov ( 1950), the Cucurbitacoae had multiplecenters of origin. As shown in figure 2, the distribution of the approxima tecenters' of orig in of th is fam ily, indicate tha t the distribution of the centersof origin of th e Cucurb ituceae is mu ch wider th an th at of D. cucurbitae.Ho wever , on th e basis of thi s informati on it is possibl e to elimina te areaswh ere D. cucurbiute does not occur, for , obviously, such ar eas cannot be

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10 H AWAII AGRICULTUHAL EX I'EHU"IENT STATION

the original home. It seems that the most likely areas must lie in the tropi­cal regions of India, Burma, Thai land, Malaya, an d, possibly, south China.

In order to nar row down fur ther the most likely ar eas where the nat ivehom e might be located , dat a on the parasite complex of this species werecompiled. This proced ure was taken on th e assumption that the fauna ofna tural enemies of a given species is richest at the center of origin. Thedata presented in table 1 indica te that th e number of species of naturalenemies of the various species of Dacus is highest in the area extendingfrom India to Mal aya. Th e data also show that the number of parasitespecies of D. cucurbita c is highest in India. These facts show that D. cucur­bitae as well as oth er species in the genus Dacus had their origin in India.

T A B LE 1. Distribution of number of parasites of Dacus spp , compared with that ofparasites of Dacus cuc urbitae Coq,

N Ul\lIlEI\ O F PAHAS ITES N UM Il E II OF I'AI\ASI T E SOF VA HlO US Dacus S1' I' . OF D . cuc urbitae

India 16 5

Thailand 6 0

Malaya 15 1

China 2 0

Formosa 6 0

Java 1 0

Born eo 2 1

Philippines 4 0

Total 52 7

From our current knowledge of D. cucurbitae, it seems most probablethat tropical south India is its home, for a number of reasons. The bio­logical characteristics of this species are not like thos e of temperate zonespecies. For example, th ere is no diapause stage (which some tephritidsof the temperate ar eas possess). Experimentally, it has been shown that,under temperate conditions, D. cucurbitae cannot complete its biologicaldevelopment (Messenger and Flitters , 1954 ) . Furthermore, with the ex­ception of th e parasite Opius uxttersi Fullaway, whi ch undergoes diapause( Marucci, 1952) , all oth er parasites do not undergo diapause and th ere­fore their distribution is restricted to tropical ar eas. The known worlddistribution of D. cucurbitae, as shown in figure 1, also indicates th at itis a tropical species.

DACUS CUCUHBITAE IN INDIA 11

According to geologis ts, the tropical peninsular portion of south India,known today as the D eccan Plateau, was once a large island and was sep ­arated from the Himalayas by a shallow sea during the Tertiary period.On th e basis of th e evide nce pr esented , it seems that D. cucurbitae and itsrelatives origin ated on thi s anci ent island.

ECOLOGICAL CONSIDERATIONS

The lit erature on the ecology of D . cucurbitae in India is very scantand fra gmen tary. The pr esent contribution, which represen ts th e resultsof my studies during 1959-60, should be regarded as an introduction tothe study of th e ecology of this tephritid fruit fly in India, wh ere the eco­system is, in many ar eas , still devoid of the drastic dis turbing influencesof modern agricultural practices.

Fi eld observations conducted during my sojourn indicated that th e gen ­eral level of abundance of D. cucurb itae in India wa s lower than the levelin Hawaii. After my expe riences with this fly in Hawaii , it was indeeda surprise to find that various cu curbits such as watermelons, can ta loupes,and gourds were being grown in India without any control measures. Ex­tensive surveys showed that the damage caused by this insect was slight,most of it occurring in localized areas , particul arl y near villages and citi es.Lawrence (1950) also reported that th e abundance of thi s insect was solow th at it was not as serious a pest in India as it wa s in oth er countries.Even though D. cucurb itae was not abundant, th ere still appeared to bea genera l increase in abundance throughout th e year in the Indo-GangeticPlains. Th e population was lowest from December to March; th en it beganbuildin g up in April and reached a peak during July to September . Duringth is latt er period, infested wild and cultivated fruits were commonly foundin th e field and also in the vegetable markets wh ere produce susceptibleto attack was sold . Furthermore, the adults were seen perched on th e low ersurface of the leaves of such plants as castor bean, Ricinus communis L. ;guava, Psidiuni guaiaoa L.; and citrus varieti es. The population began todecline in October , and, by January, th e adults had disappeared from th eirperching sites. Coinciding with th e disappearance of the adults, infestedfruits became very scarce.

Physical Environment and ActivityField surv eys and information obtained from the literature indicated that

D . cuc urbitae is wid ely distributed throughout India under extremely di­verse conditions. Although not the only important factors, temperature andrainfall are conside red in this discussion becau se th ey determin e to a lar gedegree, either dir ectly or indirectly, the gross features of the environment.

Temperature and ra infall data taken along a transect extending fromsouth to north India vary considera bly (fig. 3). In south India, monthlytemperatures vary little throughout th e year, becau se of th e maritime in­fluence. As one proceeds northward, th e monthly vari ation in tempera turethroughout the year becomes progressively greater, with higher summer

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DACUS CUCURBlTAE I N I NDIA 13

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Seasonal reproductive ac tivity of D. cucurbitae at various latitudes in India.

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temperatur es and lower winter temperatur es than in th e southern regions.In other words, th e annual temp erature extremes b ecome inc reasingly greate rin the northern areas .

Th e rainfall distribution data shown in figure 3 indica te that, with theexcep tion of Srina gar ( a city) , the general rainfall distr ibution patternswere similar , evide ntly becau se of the seasona l activity of the Indian mon­soon . Throughou t most of Ind ia, th e rainfall is generally high during Julyto October . Srina gar , situa te d in the northernmost area where th e clim ateis no t influenced by th e monsoon, was an exception, for here the h ighestrainfall occurre d during January to March.

T he seasona l cha ng es in the reproductive act ivity of D . cucurbitae ap­peared to be correlated with d ifferences in clima tic factors at variouslat it udes ( fig. 4) . In the southern latitud es, un der conditions of favorabl etemperatures, D . cucurb itae is activ e th roughout th e year. Bu t, in the nor­th ern latitudes, its period of acti vity becomes shorter du e to the decreasein the period of favorable environmental conditions .

For purposes of compa ring th e diversity of conditions between Indiaand Hawaii, a composite c1 imatograph was constructed ( fig. 5) . This clima­togr aph wa s cons tructed using th e temperature and rainfall data of 25stations from India, and 25 from Hawaii. Th e data for eac h country wereplotted and then lines demarking the extremes were drawn .

14 IIAWAIl AG HICU LTUHA L EXPEHI~IENT STATION

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The data presented in figure 5 show that, in Hawaii, D . cucurbiiaeexists under conditions of a relatively narrow range in temperature and awide range in rainfall. However, in India, th is insect exists under a widetemperature range and a slightly narrower rainfall range than in Hawaii.

Overwintering Behavior

The tolerance of D. cucurbiiae to various tempera tures has been in­vestigated by workers in Hawaii ( Keck, 1951; Messenger and F litters,1954, 1958 ) and in Formosa (Koidsumi, 1931, 19~~3; Shibata, 1936 ) . Theresults of the work of these workers are not always in agreement becauseof the inherent difficulty in determining wh en development ceased andalso probably because of the genetica lly different indiv iduals that wereused . It is possible, how ever, on the bas is of these results , to obtain ageneral picture as to the approximate temperature range in which develop­ment is poss ible. Th e lowest and highest temperature range at which thedevelopment of any of th e life stages is possible is between 50° and 100° F .Temperature ranges beyond these extremes are of common occurrence inmany parts of India where D. cucurbitae occurs.

DACUS CUCURIliTAE IN INDIA 15

The adults of D . cucurbitae were reproductively inactive during th ewinter in north India. In the Indo-Gangeti c Plains of north India, the adultswere active from about March to November. However , from December toMarch of the following year, no individuals were obs erved in the field eventhough host fruits such as lauki (Lagenaria vulgaris) and tomatoes ( L yco­persicon esculentum ) were present.

These obs ervations led to a study of the overwintering habits. Th ereappears to be a lack of agreement among Indian entomologists as to th estage in which this insect overwinters. Some have speculated that the flyoverwinters as pupae in debris, while others believe that the fly overwintersas adults.

In an effort to answer this question, field observations were conduc tedthroughout the winter . These obs ervations showed that the adult stagewas the most resistant to winter conditions. Immature stages were notfound during the winter, but the adults were noted under th e leaves offavorable plants. When th e temperature dropped below 58° F. , the adultsbecame inactive and unable to fly. Parenthetically, th ese observations cor­roborated my previous work in Hawaii which indicated that, on the slopesof Haleakala at an elevation of 3,500 feet , the adults clustered under plantleaves wh en the temperature dropped below 60° F. In the city of Pesha­war in Pakistan, Shah, Batra, and Renjhen (1948 ) also reported th at , attemperatures as low as 29° F. , th e adults overwinter under th e folds ofvarious leav es.

Ecologists classify insect development on th e basis of annual develop­mental cycles. The continuous development is called homodynamic andthe discontinuous, heterodynamic (Uvarov, 1931). My laboratory and fieldstudies showed that in south India th e development of D. cucurbiiae ishomodynamic, but that it is heterodynamic in th e north. Heterodynamicdevelopment occurs in the north because development is arrested duringwinter. However , this arrested development cannot be considered truehib ernation since the adults do not undergo complete .inactivity. Thus, th eterm "partial" or "quasi-hibern ation" appears appropriate for this type ofoverwinter behavior.

The zones, with th e respective types of development, ar e presented dia­grammatically in figure 6. This figure represents a transect along the 77°longitude extending from th e southern tip of India to Kashmir-the southto north limits of th e distribution of D. cucurbitae. From the figure pre­sented, it may be noted that south of 25° North latitude, the developmentis homodynamic. However, between 25° to 34° North latitude, th e develop ­ment is heterodynamic, for in this zone D. cucurbitae undergoes a state ofquasi-hibernation. In the ar eas north of this zone, D . cucurbitae does notoccur at all. Individuals whi ch sometimes ar e present th ere during th efavorable season ar e most likely migrants from th e southern ar eas. Thelast two zones are the peripheral or the marginal areas; th ese are th e transi­tion areas between favorable and unfavorable environments.

16 HAWAII AGRICULTURAL EXPERIMENT STATION

40NORTH INDIA.. ... . . . . .

•: .:.:.:.:- :- :.: . ZONE OF TEMPORARY

;: ;: ;:;:;:; :;: ;: ; OCCUPATION

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oFIGUHE 6. Hemodynamic and het erodynami c zones of India.

Fecundity in Summer and Winter

Because of th e wid e range between summer and winter temperatures,particularly in north India, studies on the fecundity of D. cucurbitae wereconducted , at Kanpur, India, during th ese two seasons. The genera l pro­cedure consisted of exposing ad ult flies to th e prevailing out-of-doortemperatures and recording the number of eggs laid. The food for the fliesconsisted of sugar, water, and yeast hydrolysate, the latter a product ofMarvin R. Thompson Company, Stamford, Connecticut. T he beneficial ef­fect of yeast hydrolysate on the fecundity of fru it flies in Hawaii has be enreported by Hagen and Finney (1950 ). The principal constituents of thisproduct ar e amino acids, polypeptides, and vitamin B complex.

DACUS CUCURBITAE IN INDIA 17

The summer experiments were conducted during August and September,1959, wh en th e tempera tur e ranged from 24.1 0 to 31.4 0 C. Four groups offlies, each composed of five females and five mal es, were placed ncar anop en window wh ere th ey were exposed to the prevailing temperatures.Two of th e groups of flies were fed sugar and water , and the remainingtwo, yeast hydrolysate, in addition to th e water and sugar. The numberof eggs laid by the flies in each of the groups was determined by expos­ing fruit sections of lauki ( Lagenaria vlIlgaris) for 4 hours and countingthe number of eggs laid.

The data obtained are present ed in figure 7. They show that th e flieswhich had been fed yeast hydrolysate began layin g eggs about 8 da ys afteremergence. In contrast, no eggs were laid by the flies that were fed onlysugar and water. These results ar e in agreement with the findings in Hawaiiby Hagen and Finney (1950).

25 3 0

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•DI E T• YE AS T HYDROLYS A T E

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FIGURE 7. The fecundity of D . cucurbitae under summer conditions of the Indo­Gangeti c Plains.

A comparison of the data obtained in India with those obtained inHawaii shows th e number of eggs laid by D. cucurbitae in India was low erthan the number usually laid by this species in Hawaii. The cause of thislow fecundity was not apparent from this study. Perhaps, D . cucurb itae

18 HAWAII AGRICULTURAL EXPElUMENT STATION

of north India represents strains that are inh erentl y of low fecundity. Itis also possibl e that th e high temperatures that prevailed during this periodhad an adverse effect on fecundity. That temperature did have an adverseeffect was evide nce d by th e shortened life expectancy of many of the fliesin cap tivity.

A similar study wa s conduc ted under winter conditions during Nov­ember to March at a tim e wh en th e temperature ran ged from 7° to 25° C.Four lots of flies, each with an initial number of 20 non gravid females and20 mal es, were exposed to th e prevailing out-of-door temperatures. Two lotswere fed sugar and water , and the remaining two , yeast hydrolysate inaddition to sugar and water, At various int ervals , samples consisting oftwo females were tak en from each lot of flies. The individuals were killedand ovaries and oviducts were dissected out. Th e ovaries were stained witheosin, mounted in balsam, and measured with an ocular microm eter. Inexpressing th e size of th e ovary, either volum etric or weight units ar e, nodoubt, most accurate, but in this study the width and length measurementswere used as an index of size. It was felt that this index would serve th epurpose, as this study was concerned with relative changes in th e ovariesrather th an with ab solute size .

Th e data obtained indicated that th e rate of growth of th e ovaries wa sexcee dingly low under winter conditions, and that th e ovaries fai led todevelop completely even among flies fed on yeast hydrolysate ( fig. 8) .Furthermore, th e data showed no significant differences in th e size of th eova ries between flies fed yeast hydrolysate and those that were not fedthi s proteinaceou s diet . The mean length and th e mean width of ovaries

a . ~.41l'~o·

FIG UII E 8. Mature and immature ovari es of D, cucurbi tue: a, A typ ical fully developedova ry from l O-day-old flies during th e summer; 1J, a typi cal immature ovary from3D-day-old flies during the wint er.

DACUS CUCURllITAE I N I NDIA 19

of flies fed yeas t hydrolysat e were 0.04 ± 0.001 mm . and 0.03 ± 0.006 mm.,while those of flies fed on sugar were (>.04 -+- 0.001 mm. an d 0.03 ± 0.001mm., respect ively. This lack of difference in the size of ovaries betweenyeas t hyd rolysate-fed flies and sugar-fed flies indicat es tha t th e flies didno t feed under wint er con ditions .

These studies were conducted using initially non gravid flies. Otherstudies simu ltan eou sly conducted showed that gravid individuals did laya few eggs in the middle of winter wh en th e day temperature was favor­abl e for short periods. Ho wever , the eggs fai led to hatch , du e either to lowtemperature or to th e lack of fertiliza tion becau se of low eve ning tempera­tures that were not conducive to mating.

These observations indicate that winter conditions of th e Indo-Gan geti cPlains of India are not lethal to th e ad ults. The main effect of win ter isthe suppression of ovarian development.

Habitat and Host Relations

Th e habitat of D . cucurb itae in India is similar to th at in Hawaii. Ingene ral, thi s insect fr equently occurs in cultivated areas wh ere host pl antsand other succulent nonhost plants, whi ch ar c suitabl e perching sites forthe adults , are fou nd. It also occurs in th e wilds wh ere noncultivated hostsand other suitable non host plants ar e present. Ho st plants and nonhostplants on which th e adults can perch we re th e important components ofits habitat wherever D . cucurbitae was found .

Changes in area of the habitat, which arc correlated with cha nges inclimatic factors, were obs erv ed. During Jul y to September under cond itionsof adequate rainfall , there were extensive areas suitable for D. cucurbitae.However , during th e dr y hot periods of April to Ju ne, a gene ral contractionof th e habitat occurred. This was brought about by th e drying out of theshallow-rooted herbaceous plants. Furthermore, th e destruction of th e vege­tation, during this period of food shortage, by th e feeding and tramplingof catt le and other grazing animals, was an important factor in th e eon­traction of th e habitat.

The contraction of th e habitat has an ad verse effec t on th e reproduc­tion of D. cucurb itae . Host plants and th e plants on which th e ad ul ts perchbecome separa ted; thus, th e females mu st travel conside rable distances togct to th e host plants. However , during th e wet sea son, hust plants andperching plants are close together , and th e situation is conducive to re­production .

In general , th e habitat of D. cuc urbiiae in India, although similar inregard to its basic components to th at of other countries, is not as favorableas it is in Hawaii. India is an overpopulated country and, th erefore, be­cause of th e resultant population pressure, eve ry par cel of land ha s beenexploited either by man, catt le, buffalo, sheep , horses, or goats. Thissitua tion, has no doubt had a marked effec t on th e vegetation of that coun­try. Becau se of th ese factors as well as th e clim ati c factors, a large portion

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of India now has a savannah-typ e of vegetation-a vegetation that is notsuitable to D. cucurbitae.

Th e common host plants of D. cucurbitae in th e Indo-Gan geti c Plainsand the approximate fruiting season for each are given in tabl e 2. Thistabl e shows th at , with th e exception of tomatoes, all of the hosts are in th efamily Cu curbitaceae, an observa tion that has also been mad e in H awaiias well as in oth er countries . The host list given in tabl e 2 represents someof the common host plants in India. W ith out doubt, further studies wouldreveal a conside rably larger host list th an the one presented in view of thebotanical work of Chakravarty, which shows that India has one of therichest cucurbit flora in th e world (Chakravarty, 1946 ). According toChakravarty (1959 ), th ere are 108 species of cucurbits occurring in Indiaand of th ese 38, or 35 percent, are endemic.

The availability of various hosts to D . cucurbitae throughout th e yearis shown in table 2 and figure 9. It is clear that host fru its ar e availablethroughout th e year in most parts of India. However , the number of speciesfruiting is highest during May to September , and lowest during Decemberto March.

Although the association of D. cucurbitae and its host plants in thefamily Cucurbitaceae is close, th ere is a great difference between the in­sect and host plants in th e tolerance to environmental conditions. This

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22 H AWAII AGRICULT UHAL EXl'EIUMENT ST ATION

difference is indicated by th e occurrence of some cucurbits in north Indiain w inter, wh en D . cucurbitae is no t active. This difference also becom esevident when one considers th e world distribution of th e Cucurbitacea ein rel ation to D. cucurbitae. Th e C ucurb ita ceae is a large plan t famil ywhose distribution ra nges fro m tropi cal to temperat e regions of th e world(Cbakra varty, 1959 ) . Th e distribution of th e insect , a tropi cal species,ceases, however , somew here between the sub tropic al and temperate zones.The importan ce of establishing th is imagin ary boundary has long beenrecognized , and th e work of Messenger and F litters ( 1954 ) was concernedwith this aspect of the problem.

Natural Enemies

Our knowled ge of the natural enemies of D . cucurb itae in India isbased on the work of man y entomolog ists. Bri tish an d Indian workers havemade valuable observations for many years. The foreign exploration inIndia and other areas , ma de by the Hawaii Board of Agr iculture and For­estry during 1915 to 1916 ( Clausen , 1956 ) , has also contributed to ourknowledge on this subject. Th e most tho rou gh search for natural enemiesin Ind ia wa s one undertaken wh en the Oriental fru it fly, Dacus dorsalisH endel, was discovered in Hawaii. This tremendous undert akin g was car­ried out jointl y by va rious agencies ( Cartcr , 1950; Clan cy, et al., 19.52 ) .

One of th e objectives of th e present investigati on was to study the act iv­ity of th e various parasites of D . cucurbitae. Unfortunately, parasi tes wereve ry scarce in north India. Over 5,000 larvae were sampled from ficld­collected fruits, as well as from those purchased in th e vegetable mark ets.T he only spe cies reared was Opius fictcheri Silvestri, a braconid int roducedinto Hawaii in 1916 ( F ullaway, 1916 ). In north India th e parasiti zati on bythi s species did not excee d 3 percent. This low incidence of parasit izationin north India was also rep ort ed by Ch aturvedi ( 1947), who found th atth e parasitization by O. [lctcheri never exceeded 4.5 percent.

In addition to O. [letch en, th ere are other parasites th at are known toattack D. cucurb itae in India. These are Opius ical ersi Fullnway ( F ulla­way, 1951 ); S!lnto1llosph!lrum irulicum Silvestri; Spaiangia sp. (Fletcher,1917); Lpobracon sp . (Ayyar , 1910 ) ; and Dirhinus sp . (Clancy et al., 1952 ).

The re ason for th e low incid ence of parasitization in north India is notclear. F ield observations indicate that unfavorable climate is one of th eimportant factors. Nor th India is a marginal area for D. cucurbitae as wellas for its parasites. The overwinterin g in the adult stage is not conduciveto th e survi val of th e parasites which attack th e immature stages of th eirhost. Opius ioatersi is, eviden tly, th e only parasite adapt ed to north Indiancond itions, for it undergoes diapause during th e winter months ( Marucci,1952 ) . But even though it appears to be ad apted to northern conditions,thi s parasite wa s no t abundant in north India.

DACUS CUCURBITAE IN INDIA 23

DISCUSSION

Th e distribution of D. cucurbitae in Ind ia extends from th e southerntip to the northern most bo undaries. The south to north distrib ution is, there­fore , larger th an th at in any oth er sing lc country in the world. Here, thena tural population of D. cucurbitae is found in tropical, subtropical, and,to a certain extent, temperate latitudes. Thus, India is without doubt oneof the most interesting ar eas to study the zoogeography and ecology ofD . cucurbitae under natural conditions.

Th e occurrence of D . cucurbitae in Srin agar , 35° North latitude, rep­resents the northernmost distribution of th is insect. It is not known , how­ever, wh ether or not it overwinters at this latitude. The nor the rnmost are awhere D . cucurbitae is known to overwinter is in Peshawar, West Pakistan,about 200 miles southwest of Srin agar. In Peshawar thi s insect has beenobs erved to overwinter as adults at temperatures as low as 29° F . ( Shah,Batra, an d Renjhen , 1948 ). It is possible that migration into Kashm ir Valleyoccurs annua lly from Peshawar; however , further investigations are neces­sary before final conclusions can be drawn.

The dispersal of D. cucurb itae from south India, its original home, toth e northern ar eas must ha ve been a gradual process. In some respects,this northward dispersal does not seem difficult because of the contiguousland mass and th e wide distribution of the fly's host plan ts . Man, no doubt,played an importan t role in hasten ing this process by tra nsporting infestedmaterials from one place to another. In other respects, th ere must havebeen clima tic barriers becau se of the changes that occur with la titu de.This penetration of these ecologic barriers must ha ve been a gradualprocess, one which invo lved th e development of stra ins adapted to no rth ernconditions- in a manner similar to that of Dacus tnjoni in Australia (A ndre ­wa rtha and Birch, 1960 ) .

The general level of abundan ce of D . cucurbltae was found to be mu chlower in India than in Hawaii. E ven th ough quantitative evidence is lack­ing, it might be desirab le to discuss some of the possible factors whichinfluence the population in India. It must be real ized that D . cucurbitaein India is only a small component of a complex ecosystem and that am ultitude of interacting factors arc involved.

Natural enemies, no doubt, play an important ro le in keeping th e po pu­lati on down even though the percentage of parasitization is lower thanthat in Hawaii. The occurrence of a number of species of parasites in spi teof th e low host density is remarkable.

The chang ing characteristics of the hab ita t are also an important fac­tor. The habitat can support a mod erat ely high popul ati on only for a shor tdurati on during th e wet season which occurs during Jul y to Sep tember.During thi s time host fru its ar e abundant. Adult food in the form of honey­dew from horn opterous insects and glan du lar secretions from various plant sis also abunda nt. These plants also serve as sheltering sites where the adultsare protected against sun, wind, and rain . H owever , these favorabl e con-

24 H AWAII AGIUC ULTUHAL EXPERIMENT STATION

ditions do not last very lon g, for with th e onset of th e dry period s most ofth e fav orable plants die from drou ght. Furthermore, du e to food shortage,mu ch of th e habitat is destroyed by foraging animals including cattle , buf­faloes, sheep, goats, and hors es.

Another important consideration is th e unhealthy structure of th e eco­system. India, being a land of scarc ity, is a land wh ere th e number ofprimary producers is small in relati on to th e number of cons umers . Ap­proximat ely 80 percent of th e people are eng aged in agri cultural produc­tion ; ye t, th ere is a shortage of food. Food is also scarce for an imals suchas ca ttle, buffaloes, goats, sheep, horses, monk eys, and birds. Under suchcond itions, almo st every fruit produced is consumed eithe r by man or byother animals. The ultimate effect of thi s population pressure is host scarcityof D . cucurbitae. Ho st scarc ity leads to competition for food among othersp ecies of cucur bit-feeding Tephritidae, such as Da cus ciliatus, V . hageni ,and MyoparcZalis partlalina, which have similar host re quiremen ts. Thecompetition ph enomenon among th ese cucurbit-infesting tephritids has notb een studied pel' se. However , th e results reported by Chaturvedi (1947 )indicate that th ere is competition bet ween D. ciliatus and D . cucutb itae.

Finally, th e adverse effe cts of temperature extremes on th e populationwill be bri efly considered . Temperature extremes in india are large, part ic­ularly in the northern areas where the temperature may drop to freezingor lower in winter and may rise as high as 110 0 - 115° F. in other seasons.These extreme s, which are far b eyond th e thresholds of development (Koid­sumi, 1931, 1933; Shibata, 1936; Keck , 1951; Messenger and Fl itt ers, 1958 ) ,no doubt cause considerable mortality, particul arl y in th e immature stages.Although adults can surv ive th e winter conditions of th e northern areasof India, their mating is adv ersely affected . For example , during Novem­b er th e day tem peratures in Kanpur were favorable for adult activity;however, the twiligh t temperatur es were too low for ma ting, which takesplace soon after sundown. Becau se th e evening temp erature, wh ich wa sbelow 60° F ., was not conducive to mating, ad ults in cap tivity laid infertileeggs.

Th is study represents a preliminary study on th e field ecology of D.cucurbitae in india, an excee ding ly fertile country for th e study of ma nytephritid fru it flies. A study of th ese fly sp ecies, many of which arc ofconside rable economic imp ortance, should be undertaken in India, for itis through such a study that a thorou gh understanding can be obtainedof their ecology in th eir na tive habitat s. If we expe ct to understand th eecology of tephritid fruit flies in th eir exotic habitats, we must first under ­stand th eir ecology in th eir native habitat s. This general idea has beenelucidated in a thought-provoking arti cle by Doutt ( 1961) .

DACUS CUCURBITAE I N I NDIA

SUMMARY

25

This study was concerned with certa in aspects of th e zoogeography andthe ecology of D. cucurbitae . It was conducted during 1959-60 with head­quarters at the Govern ment Agricultura l College, Kanpur, India.

Th e present world distribution of D. cucurbitae is not extensive. It hasbeen reported from India, Burma, Malaya, the Philippines, southern China ,Ceylon, Pakistan , Formosa , Okinaw a and the nearby islands , Kenya, Ma uri­tius, Saipan, Guam, and Hawaii . These areas are within 35° North and 22°South latitudes, whi ch include th e tropical , subtropical, and frin ges of thetemperate zones. Evi de nce ba sed on host pr eferences, natu ral enemy com­plex, and general biology indicated that th e na tive home of D. cucurbitaeis south India.

Th e duration of the period of reproductive activity of D. cucurb itaevaried throughout India. In south India, reproduction conti nued through­out th e year; however , as one proceed ed northward the durat ion of th ereproductiv e activity became shorter. These changes were correlate d withclim ati c differences.

In north India, D. cuc urbitae overwinters in th e adult stage. The ovariesof the overwintering individuals remained undevelop ed for periods as lon gas 4 months. Under field conditions , adults have been report ed to over­winter at temperatures as low as 29° F .

E xpansion and contraction of th e habitat were observed . Th e expansionoccurred from Jul y to September under conditions of ad equate rainfallbrought by the mon soon . The contraction occur red during the dr y period.The activity of foragin g animals, including cattle, sheep , bu ffaloes, horses,and goats, hastened thi s process. The populati on of D. cucurbitae appearedto be correlated with changes in habitat .

Plants in th e family Cucurbitaceae are the principal hosts of D. cucur­bitae. Of th e 19 common hosts list ed, 18 belong to th e Cucurbitaceae .Because of th e rich cucurbit flora of India, the host list of thi s insect isbelieved to be conside rably longer than that rep orted in thi s pap er.

Six species of parasites are kno wn to attack D . cucurbitac in India.These are Opius jletcheri Silvestri , O. icat ersi Fullaway, Sijntom osplujrum.isulicum Silvestri , Spalangia sp. , and Ip obra con sp. The most abundantspe cies wa s O. [letcheri, th e pred omin ant parasite of D . cucurbitae inHawaii.

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ANDREWAHTlIA, H. G., and L. C. B IHCH . 1960.SOME HECE NT CONT HIIlUTION S TO THE STUDY 01' THE DISTIUBUTION A ND ABUNDANCE

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26 HAWAII AGRI CULT URAL EXPERIMENT STATION

B ACK, E. A ., a n d C . E. P E MIIEHT ON . 1914.LI F E I lI ST OH Y OF T IlE M ELON F LY. ]. A gr. Res. 3( 3 ) : 269-274 .

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_ _ 1959.MONOGHAPII ON INDIAN CUCURlllTACEAE. Bot anical Surv ey I n d i a 17 ( 1) : 1- 234.

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DACUS C UCURIllTAE I N I ND L\ 27

K OIDSUMI, K. 1 9 31.EXPEIUl\IENTA L STUDIES ON TIlE I N F LUENC E OF LOW TEMPEIIATUHES UP ON T HEDEVELOPMENT OF F IIUIT FLIES. FJHST II EP OHT . ON THE FATAL ACTION OF LOW TEMP­EIIATUII E UP ON T IlE PUPAE AND LAIIVAE OF TIlE MELON FLY (Cluictodacus cucurbi­tae ), Bull. D ept. A gr. , Govt. Res . I n s t. , Taihoku, J apan . No. S5.

__ 193 3.

EXPElIlMENTAL STUDIES ON T IlE INFLUENCE OF LO W T EM P EI IATUIl ES UPON THE DE­VE LOPMENT OF FIIUIT FLIES. TIIlHD II EP OIlT . ON TIlE VELOCITY, FAVOIIAIJLE T EMPE HA­TU HE, AN D TIIlIESIIOLD OF DEVELOPMENT OF PUPAE, EGGS , A ND LAIIVAE OF MELONFLY, Cluietodacus cucurbitae COQUI L LETT . J . Soc . Trop . Agr , Formos a 5(2) :

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_ _ an d __ 195 5 .

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28 HAWAII A GRI CULTURAL EXPERIMENT STATION

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UNIVERSITY OF HAWAIICOLLEGE OF TROPICAL AGRICULTURE

HAWAII AGRICULTURAL EXPERIMENT STATIONHONOLULU, HAWAII

THOMAS H. HAMILTONPresident of the University

MORTON M. ROSENBERGDean of the College and

Director of the Experiment Station

G. DONALD SHERMANAssociate Director of the Experiment Station