Food-deprived Drosophila melanogaster extend their proboscises following sucrose stimulation of the front tarsi (the proboscis extension reflex). Medioni and Vaysse (1975) reported that the inhibition of this response can be conditioned over trials if such proboscis extensions are punished by applying an aversive stimulus to the foreleg tarsi. In this study, Medioni and Vaysse's basic observations of conditioning were replicated, with a different strain of flies and a modified conditioning apparatus.

Mating behavior in the fruit fly, Drosophila, has been studied extensively (Ehrman and Parsons 1976). It is known, for example, that females of many species in this genus copulate repeatedly both in the laboratory (Pruzan 1976;

Summary. White-eye Drosophilapseudoobscura males display a deficiency in their mating ability in the light, although they are able to mate readily in the dark. The present data suggest that the mating deficit is due to a neurobehavioral disruption produced by faulty visual input.Drosophila species exhibit different degrees of light dependency in their mating behavior. Grossfield 1 contends that Drosophila species which mate equally well in the light or in the dark are able to adjust their behavior, especially their mating behavior, in order to adapt to varying environments. Both Drosophila melanogaster and Drosophila pseudoobscura are widely distributed species with such light independent mating behavior. Mating behavior in the light is disrupted in pigmentdeficient D. melanogaster mutants. Connolly et al. 2 found that white-eye D. melanogaster males exhibit a significant decrease in the mean bout length of wing vibration during courtship under lighted conditions. Previous investigations showed that eye pigment-deficient mutant flies in D. melanogaster display decreased abilities in pattern contrast for both movement and form perception 3. This suggests that the impaired contrast perception of the white-eye males may prevent these males from establishing contact with the females. Indeed, Connolly et al) hypothesized that the female receives less stimulation from the white-eye male so that longer courtship time is needed for copulation to occnr.We found that white-eye D.pseudoobscura males also show a decrease in their mating ability under lighted conditions. 3-and 4-day-old virgin white-eye Arrowhead double mutants (or, pr; homozygous on the 3rd chromosome for both orange and prune) were allowed to mate under the following conditions.