The role of floral scent of the cherry tree, Prunus yedoensis, in the foraging behavior of Leuhdorfia japonica (Lepidoptera : Papilionidae)

The olfactory response of adults of Luehdorfia japonica (Papilionidae) to f loral volatiles from Prunus yedoensis (Rosaceae) was investigated by means of a behavioral test (reflex extension of proboscis: REP) and electroantenn ographic (EAG) responses. Chemical analysis of the flower extract revealed that the floral scent consisted mainly of aromatic compounds, among which b enzaldehyde (BAL, ca. 33%) was the dominant component. Of 10 floral volatil es tested, phenylacetaldehyde (PAL) elicited the highest REP response from both sexes. The REP-eliciting activities of benzyl alcohol, 2-phenylethanol and BAL, though a little lower than that of PAL, were also relatively high (ca. 50%) compared with those of other floral components. These four compo unds, therefore, were considered to be the olfactorily active principles th at stimulate foraging behavior in the butterfly. In EAG experiments with te n test chemicals, differences in responsive intensities among these compoun ds were not remarkable at a dose of 1 mu g In contrast, males displayed str onger EAG responses to ethyl phenylacetate, linalool, BAL and PAL at a dose of 100 mu g. The present findings indicate that the antennal sensitivity o f the butterfly is not necessarily correlated with the REP behavior. Althou gh we found no explanation for conspicuous male EAG responses to particular components, this phenomenon seems suggestive of additional and as yet unkn own function(s) of these compounds in the life of the male butterfly.