Behavior genetics of olfactory responses in Drosophila. I. Olfactometry and strain differences in Drosophila melanogaster.

A simple olfactometer was constructed for measuring the responses of adult Drosophila to odoriferous substances, and an index (attractability index, AI) is proposed to evaluate the response. Five strains of Drosophila melanogaster of different geographic origins were tested for their responses to five chemical attractants: ethyl alcohol, acetic acid, lactic acid, ethyl acetate, and n-butyraldehyde. Statistical analysis has shown that the differences of AI among strains are highly significant for all the odorants except acetic acid and that male flies are, in general, less sensitive than females. The number of flies which were inactive in the olfactometer also varied with strain, sex, and odorant, suggesting the involvement of some other behaviors, and this raises some difficulties in interpreting the heterogeneities of AI. Nevertheless, these results suggest that a considerable amount of genetic variation for olfactory response exists in natural population of D. melanogaster.