Abstract: To study the roles of olfaction and vision in the food searching behavior of insects, we investigated the number of trapped adults of Drosophila melanogaster with bayberry and orange as attractants, and the effect of pretreatment with olfactory fruits (bayberry or orange) during the behavioral scenario. The results showed that traps with visual and olfactory cues from the same fruit sources attracted more flies than the bayberry picture or olfactory odor from the bayberry. However, the flies attracted by the combination of visual and olfactory cues from different kind of fruits were not significantly more than those attracted by olfactory cues. Experience by olfactory pretreatments with fruit bayberry or orange not only increased the number of flies attracted by olfactory or visual cues, in which the number of flies attracted by olfactory bayberry was the same as that attracted by bayberry with visual and olfactory cues, but also increased the number of flies attracted by traps with visual and olfactory cues from different kind of fruits. However, olfactory pretreatments did not influence the number of flies attracted by traps with visual and olfactory cues from the same fruits. So, olfactory and visual cues were used by flies in food searching behavior and there was synergistic effect of visual and olfactory cues from the same fruits on the attraction of flies. The fly D. melanogaster has strong memory, and can use remembered olfactory cues to facilitate food searching. Our results will not only improve our understanding about the food searching behavior of flies in nature, but also help us to design more efficient fly traps.

Key words: Drosophila melanogaster, vision, olfaction, synergism, food searching