Mass Rearing of Three Species of Hippelates Eye Gnats (Diptera: Chloropidae)1

Abstract

Simplified procedures for rearing Hippelates eye gnats in the laboratory are described, H. collusor (Townsend) has been reared successfully for over 50 generations; H. robertsoni Sabrosky and H. pusio Loew, both not colonized before, have been reared tor more than 25 generations. Efforts to colonize H. dorsalis Loew have been only partially successful, and mass rearing has not been ac-complished. All colonies were maintained at 80°-85° F. and 20%-40% r.h. During weekdays 4 man-hours daily were required for complete care of the colonies of the three species and a resistant-strain colony of H. collusor ; on weekends only 2 man-hours daily were needed. Adult gnats were fed from absorbent dental rolls that had been impregnated with the food solutions, and lived longer when fed from rolls that were dried than when the food was given them in solution. On dry diet containing proteins, carbohydrates, minerals, vitamins, cholesterol, and fat they lived beyond their 5- to 7-day preoviposition period and laid many eggs; on the same diet in solution they lived only a short time beyond the preoviposition period and laid very few eggs. Proteins and carbohydrates were essential for production of maximum numbers of hatchable eggs; gnats fed on honey or sugar alone produced hatchable eggs in small numbers, but probably the solutions contained or were contaminated with small amounts of protein. That autogenesis occurred is also suggested, but present information was inadequate to verify this. Parthenogenesis does not occur in H. collusor , a species studied extensively. Its unmated females produced eggs that failed to hatch, while mated females from the mixed laboratory populations produced fertile eggs with 70% hatchability and with 76% average viabilities at 80° F. and 100% r.h. For eggs of H. pusio and H. robertsoni average viabilities were indicated as 72% and 80%, respectively, under these same conditions. Sex ratios of the emerging gnats under uncontrolled conditions were not consistent, with females outnumbering the malts in some observations but not in others.