Hagen, K.S.

Proceedings of the Hawaiian Entomological Society

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Vol. XV, No.1, March, 1953 115A Premating Period in Certain Species of the Gnus Opius(Hymenoptera: Rraconidae)By KENNETH S. HAGENDEPARTMENT OF BIOLOGICAL CONTROL. UNIVERSITY 0 CALIFORNIAThe majority of species belonging to the genus Opi s that parasitizevarious tephritid species in the Hawaiian Islands will ate immediatelyafter emergence. However, in two Op,us species a disti t period of timemust elapse after emergence before the males will copu ate. This periodis designated by the author as the premating period.It is well known that the males of all the species discu sed herein beginemerging before the females. This differential in emerg nee may at timesbe two days in length. However, with the exception . the two specieshaving the premating period, when the newly emerged ales are exposedto females of a different brood they will copulate imm diately.The species Opius humilis Silvestri, O. tullawayi (Silvestri), andO. tryoni Cameron, parasites of Ceratitis capitata (W edemann), mateimmediately after emergence (Back and Pemberton, 918; Pembertonand Willard, 1918). The melon fly parasite, O. tletche i Silve~tri, showsthe same behavior (Willard, 1920).' Another parasite of Dacus cucur-bitae Coquillett, O. watersi Fullaway, and the parasi s of D. dorsalisHendel, O. longicaudatus (Ashmead) and O. tormosan s Fullaway, wereobserved to copulate just after emergence.The two species in which the males apparently req ire a prolongedperiod after emergence before they will copulate are O. ophilus Fullawayand O. vandenboschi Fullaway. These species are parasi es of the orientalIruit fly, D. dorsalis, and differ from the above-men 'oned species byovipositing in the host eggs (van den Bosch, et al., 19 I) or in the firstinstar larvae (Bess, et al., 1950), respectively, rather han in the largelarvae.A study of the adult male internal reproductive sys ms 01 these twospecies revealed different degrees of spermatozoan migr tion through thegenital ducts dependent upon age. In newly emerged m les the only free,active spermatozoa were confined to the testes near the bases of the vasadeferentia. After five or six days at a mean temperatu of about 80°F.,dissections showed the spermatozoa to have reached the esicula seminalis.It is not until the spermatozoa have reached this poi t that the malesshow any observable sexual behavior.If both sexes of either O. oophilus or O. vandenbose i are allowed toremain together for five or six days after emergence t ey still may notcopulate. However, if the sexes are kept separate for fi or six days andthen mixed, a mating behavior occurs immediately. The absence ofInating in the former case where the males were sexu lIy mature is ap-116. Proceedings, Hawaiian Entomological Societyparently associated with a lack of an attractant gradient between sexes.An obliteration of gradients between sexes is perhaps the result of airsaturation of sexual odors. This hypothesis is supported by the fact thatwhen carbon dioxide or even fresh air is blown through the cage, amating reaction occurs (£lipping of wings, Whiting, 1932) and mating isstimulated soon after the cessation of the £low of the CO2 or air. It wasfound that the males of all the Opius species studied have internal glandswhich originate in the pygidium. A faint oblique line near the lateral.posterior angles of the pygidium can be seen externally. These glandsapparently differ interspecifically. An odor evidently from these "scentglands" is perceptible to humans.LITERATURE CITEDBack, E. A.' and C. E. Pemberton.1918. The Mediterranean fruit fly in Hawaii. U. S. Dept. Agr. Bull. No. 536 (Prof.Paper). 118 pp.Bess, H. A., R. van den Bosch, and F. Haramoto.1950. Progress and status of two recently introduced parasites of the oriental fruitfiy,-Dacus'doTsalis Hendel, in Hawaii. Proc. Haw. Ent. Soc. 14(1) :29-33.Pemberton, C. E. and H. F. WilIanI.1918. A contribu.tion to the biology of fruit fly parasites in Hawaii. Jour. Agr. Res.15 (18) :41~-465.van den Bosch, R. and F. H. Haramoto.1951. Opius oophilus Fullaway. an egg.larval parasite of the oriental fruit fly dis-covered in Hawaii. Proc. Haw. Ent. Soc. 14 (2) :251-255.Whiting, P. W.1932. Reproductive reactions of sex mosaics of a parasitic wasp. HnbrobTCJconjug/andis. .Jour. Comp. Psych. 14:345-363.Willard, H. F.1920. 0Pius fletcheri as a paraSite of the melon fly in Hawaii. Jour. Agr. Res.20 (6) :423-438.

A Premating Period in Certain Species of the Genus Opius (Hymenoptera: Braconidae)

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A Premating Period in Certain Species of the Genus Opius (Hymenoptera: Braconidae)

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