Male sexual maturation of the tsetse fliesglossina morsitanswestwood andg. austeniNewstead (Dipt., Glossinidae) in relation to blood feeding

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Abstract
The effect of blood feeding on male sexual maturation in the tsetse flies Glossina morsitans Westwood and G. austeni Newstead was studied by comparing copulation and insemination performance of unfed and fed males during the first five days of adult life. These species differed conspicuously, both in the course of maturation and in the influence of blood feeding on it. G. morsitans males copulated before they could inseminate, and even fed flies did not all inseminate until day 3; unfed flies showed retarded insemination performance by day 2, before copulation performance declined. G. austeni males were less sexually responsive at first, but they nearly always inseminated when they did copulate, even on day 1. Unfed flies showed less increase in copulation performance by day 4, but no decline. Accessory glands were larger in G. austeni than G. morsitans at emergence, and in unfed flies of both species they ceased to grow after day 3. Both accessory gland size and copulation duration (beyond a minimum duration) were related to insemination success in a general way, though copulation duration was quite variable. Vertebrate blood apparently provides male tsetse with specific nutrients or stimuli which promote sexual performance, in addition to basic energy and water requirements. Feeding probably affects insemination in G. morsitans through accessory gland development, allowing more complete spermatophore formation and sperm transfer, but its mode of action on G. austeni sexual responsiveness is not evident.