GENETICS OF FOOD PREFERENCE IN DROSOPHILA-SECHELLIA .1. RESPONSES TO FOOD ATTRACTANTS

To reveal the genetic mechanism of host selection in a monophagous fru it fly Drosophila sechellia, olfactory responses and oviposition prefe rences of this species were compared with those of closely related pol yphagous species, D. simulans and D. melanogaster. Adult flies of D. s echellia were strongly attracted to the ripe fruit of Morinda citrifol ia which is known to be the sole breeding site of this species. They w ere also attracted to the odor of n-caproic acid which is contained in the ripe fruit of M. citrifolia and is presumably responsible for the characteristic odor of the fruit. In contrast, D. simulans and D. mel anogaster showed a strong repulsion to n-caproic acid. In parallel wit h the olfactory responses, D. sechellia females laid eggs preferential ly on a medium containing n-caproic acid, to which the other two speci es showed an aversion. Genetic analyses using the hybrid progeny betwe en D. sechellia and D. simulans suggested that the species differences in these behaviors are controlled by gene(s) located on the second ch romosome.