The maintenance of sexual isolation between four sympatric species of the D. virilis group

The courtship behaviour of four sympatric species of the Drosophila virilis group was studied in the wild, with most observations made at baits of fermenting malt. The males courted the females of both their own and alien species, but only intraspecific courtships occasionally led to a copulation. Nearly all of the interspecific courtships broke off when the female began to vibrate her wings or flew away shortly after the male had begun to make courtship sounds.