OVULATION AND THE SUPPRESSION OF MATING IN DROSOPHILA-MELANOGASTER FEMALES - BEHAVIORAL BASIS

Virgin females of Drosophila melanogaster that are ectopically express ing the sex-peptide gene show a high level of ovulation and are unrece ptive to males. However if they are genetically deprived of eggs, rece ptivity is considerably restored (Fuyama, 1995). These females, whethe r they have eggs or not, extrude their ovipositors toward courting mal es as frequently as do fertilized females. However, this rejection beh avior was ineffective in suppressing male courtship. Of females with e ggs, about half of them could suppress male courtship. Females lacking eggs could not suppress male courtship and continued to elicit vigoro us courtship. This difference seems to account for the increased matin g frequency in sterilized females. Courtship behavior by mutant males defective in olfaction or learning suggested that females are capable of repelling males by emitting a volatile pheromone(s) with an inhibit ory effect on male courtship.