ABSENCE OF DIRECT SEXUAL SELECTION FOR PARASITOID ENCAPSULATION IN DROSOPHILA-MELANOGASTER

Resistance against parasites may play a role in female mate choice, es pecially if males that have actually survived parasitism can be discri minated from males that have not been parasitised. Larvae of several D rosophila species are subject to attack by hymenopteran parasitoids, b ut have the ability to kill the parasitoid egg through the process of encapsulation. Because an encapsulated egg remains visible in the abdo men of the adult fly throughout its life, its presence in a male signa ls to a female that the male has the genes to survive parasitism. The hypothesis that females preferentially mate with males bearing an enca psulated egg in their abdomen was tested using D. melanogaster. No ind ication was found for this female preference. The absence of preferenc e for males with ''good genes'' could result from sensory constraints in the female or a negative correlation between encapsulation ability and some other fitness component. Alternatively, it is hypothesised th at the black abdominal ends of the males of many species in the melano gaster-group evolved to mimic encapsulated eggs, leading to the breakd own of capsule recognition by the female.