836 X\NNALS OF THE ENTOMOLOGICAL SOCIETY OF AMERICA [Vol. 60, No. 4 tory, natural enemies and the poisoned bait spray as a of the Diptera of America North of Mexico. USDA method of control of the imported onion fly (Phorbia Agr. Handbook 276. 1696 p. scpctorum Meade) with notes on other onion pests. Vos de Wilde, B. 1935. Contribution a l'etude des lar- J. Econ. Entomol. 8: 342-50. ves de Dipteres Cyclorraphes, plus specialament des Steyskal, G. C. 1947. The genus Diacrita Gerstaecker larvae d'Anthomyides. (Reference in Hennig 1939, (Diptera, Otitidae). Bull. Brooklyn Entomol. Soc. p. 11.) 41: 149-54. Wahlberg, P. F. 1839. Bidrag till Svenska dipternas 1951. The dipterous fauna of tree trunks. Papers Kannedom. Kungl. Vetensk.-Akad. Handl. 1838: Mich. Acad. Sci., Arts, Letters (1949). 35: 121-34. 1-23. 1961. The genera of Platystomatidae and Otitidae Weiss, A. 1912. Sur un diptere du genre Chrysoviyaa known to occur in America north of Mexico (Diptera, nuisable a l'etat de larve a la cultur du dattier dans Acalyptratae). Ann. Entomol. Soc. Amer. 54: 401-10. l'Afrique de Nord. Bull. Soc. Hist. Nat. Afrique 1962. The American species of the genera Melieria Nord. 4: 68-69. and Pseudotcphritis (Diptera: Otitidae). Papers Weiss, H. B., and B. West. 1920. Fungus insects and Mich. Acad. Sci., Arts, Letters (1961) 47: 247-62. their hosts. Proc. Biol. Soc. Wash. 33: 1-19. 1963. The genus Notogramma Loew (Diptera Acalyp- Wolcott, G. N. 1921. The minor sugar-cane insects of tratae, Otitidae). Proc. Entomol. Soc. Wash. 65: Porto Rico. J. Dep. Agr. Porto Rico. 5: 46 p. 195-200. Zetterstedt, J. W. 1847. Diptera Scandinaviae. 6: 2163 1965. Otitidae p. 642-54. In A. Stone et al. A Catalog 2580. Some Irradiation Studies and Related Biological Data for Culicoides variipennis (Diptera: Ceratopogonidae)1 ROBERT HENRY JONES2 Entomology Research Division, Agricultural Research Service, USDA, Kerrville, Texas ABSTRACT Colony specimens of the biting midge Culicoides vari- creased, but even 30,000 R failed to sterilize completely. ipennis (Coquillett) were treated with gamma radiation Treated females did not recover and rarely laid more than as larvae, pupae, and newly emerged adults at 5000, 10,000, 1 egg batch, though those batches that were laid often had and 15,000 R, and as pupae at 20,000 and 30,000 R. The rather low percentages of sterility. With treated females, criterion for the sterility of males was the hatch of eggs the number of eggs per egg batch decreased as the radi- deposited by untreated females with which they mated. ation dose increased, until at 30,000 R no eggs were laid. Males treated at doses above 5000 R were, with few ex- Miscellaneous biological information for colony C. rari- ceptions, 95%—100% sterile in first matings, but males ipennis, principally relating to reproductive performance, treated at all levels tended to recover fertility in later was obtained in testing the treated specimens and the matings. Recovery decreased as the radiation dose in- accompanying controls. The biting midge Culicoides variipennis (Coquil- worm fly, Cochliomyia hominivorax (Coquerel), lett) is a common and sometimes serious pest of from both the Southeastern and Southwestern United livestock. In addition, Foster et al. (1963) indicated States, and is being used with several other insect that the species is a vector of bluetongue disease of species (Smith 1963). sheep in the United States. Nevertheless, C. vari- In the winter of 1961-62, I had the opportunity to ipennis, like most Culicoides, has not been very thor- study the effects of gamma radiation, the sterilizing oughly studied. Our knowledge of its biology is agent used for the screw-worm fly, on C. variipennis. fragmentary, and few practical methods have been At that time, a colony (Jones 1966) was being main- proposed for large-scale control if it should become tained at Kerrville, Texas, at the same time a cobalt80 necessary. The larval habitats of the species are source was available there (Jefferson 1960). It was diverse (Jones 1961), and although the large breed- thus possible to investigate the general patterns of ing sites that sometimes occur in very favorable areas radiosensitivity for the species, and at the same time can be located and treated with insecticides, typical to gather some miscellaneous biological information. sites are small and occur in such obscure places that it would be virtually impossible to find and treat MATERIALS AND METHODS them all. Under these circumstances, 1 method of control to consider would be the sterile-male tech- In an experimental program designed to test effects nique, in which artificially sterilized individuals are on reproduction, certain biological characteristics of released throughout the mating season in numbers C. variipennis tend to make handling procedures large enough to overwhelm the native population, rather involved. The life cycle is short—at the time thereby greatly reducing the number of offspring of this work, with colony specimens (C\ v. sonorcn- available for each succeeding generation. This tech- sis Wirth and Jones, isolated December 1957) the nique has been successful in eradicating the screw- egg developed in about 2 clays, the larva in 16 days, and the pupa in 2^2 days. Because of the short pupal stage, test pupae had to be separated on the 1 Accepted for publication October 3, 1966. 3 Present address: Livestock Insects Investigations; Entomol- basis of quite small differences in age so that there ogy Research Division, ARS, USDA; Building 45, Denver Federal Center; Denver, Colo. 80225. would be enough groups for comparison. Sexual July 1967] JONES : IRRADIATION OF Culicoides variipennis 837 development in the species occurs very early, and during a single period, the flies were separated at 4- mating is commonplace in cages of colony adults 12- hr intervals as usual, but were later combined with 24 hr old. (Before setting up this study it was deter- flies that had emerged slightly earlier or later). For mined that adult males as young as 8 hr old can suc- adults, age at treatment was designated by the num- cessfully inseminate females, and that females as ber of hours after emergence; for immature forms, young as 4 hr old can be inseminated.) In addition, by the number of hours between irradiation and emer- both sexes can mate repeatedly and remate immedi- gence—thus, pupae in a 12- to 8-hr emergence group ately. However, even though mating frequently oc- were more nearly mature at irradiation than those in curs in cages that contain numerous adults, it is not a 28- to 24-hr group. certain, or even likely, that a standard percentage of The day after emergence, groups of females were females in such cages will be inseminated, and to given their first blood meal (on the belly of a rabbit) guarantee mating it is necessary to isolate a pair and and those that engorged fully were then used for induce copulation. For these reasons, the sexes had mating. A female and a male were drawn into a IX to be separated within about 4 hr after emergence to 3-in. aspirator vial and gently tapped together to in- prevent undesired matings, the adults had to be duce copulation. The time in copula was recorded mated a pair at a time, and each adult had to be for each mating, and the pair was separated immedi- uniquely designated and handled as an individual. In ately afterward to prevent remating. After mating, ('. t'uriipcmiis the female is nonautogenous, and ap- each individual was caged separately in a standard parently without exception requires a blood meal for holding cage made of a J^-pt ice cream carton with a each batch of eggs deposited. Although she can use cloth lid. A homeopathic vial was inserted through a sperm from more than 1 mating, she can also store hole in the side to provide liquid through a cotton enough sperm from a single mating to fertilize sev- wick. Cages for males had plain cardboard bottoms; eral egg batches. Thus, to determine the permanence cages for females had holes in the bottom fitted with of any sterility induced, test females had to be given small plastic dishes containing moist cotton covered a series of blood meals to permit recovery of a series with circles of paper toweling for oviposition (these of egg batches and test males had to be mated over a same cages served as emergence cages when pupae period of time with a series of untreated females. were placed on moist cotton in the plastic dishes). The first tests were conducted at 5000 and 10,000 All flies received an alternating diet of 5% honey solu- R. When these doses did not completely sterilize, tion for 1 day and distilled water for 2 days, but the further tests were conducted at 15,000, 20,000, and females began their first day with water and the 30,000 R. Just before irradiation, each test group to males with honey. For later blood feedings, a female be used was divided in half, and 1 of the halves was was transferred to a feeding cage and then returned kept untreated to serve as normal controls; these to her holding cage. In feeding procedures, the fe- normal specimens were handled throughout the test male was always observed for engorgement, since in exactly the same way as the treated ones. Only mere presence in a feeding cage did not automatically flies from the same test and age group were mated mean that she would take a blood meal. with one another, and each mating series began with Females almost invariably laid their eggs during all 4 of the possible combinations between the treated the night, attaching them to the circles of paper (T) flies and their corresponding normal (N) con- toweling.