Food volatiles as attractants for yellowjackets (Hymenoptera: Vespidae)

Assays with a captive Vespula germanica (F.) colony indicated that foragers were more strongly attracted to Dear. aged 24 h than to 0- or 48-h-aged pear. Sixteen chemicals found in 24-h pear and other foods were tested for their attractiveness to social wasps in a series of four trapping trials in rural and urban settings in Wisconsin. Workers of V. germanica, V, maculifrons, Dolichovespula maculata (L.), and Polistes fuscatus (F.) were most strongly attracted to isobutanol with 0.5% acetic acid added to the drowning solution, confirming previous work. We report for the first time that males of V. maculifrons were trapped in significant numbers by the isobutanol + acetic acid combination. None of the tested compounds found in ripe pear was shown to be especially attractive to V. germanica or V. maculifrons workers or males. However, 2-methyl butanol, a compound similar in structure to isobutanol, was found to attract V. germanica and V. maculifrons workers as well as V. maculifrons males. Furthermore, V. vidua (Saussure) differed. from the other species in that it was not attracted to the isobutanol + acetic acid combination, but was caught in traps baited with 2,4-ethyl decadienoate. This supports earlier evidence suggesting that vespine species are not all alike in their responses to olfactory cues. Our results, taken together with previous work, indicate that some food-borne volatiles may modulate the stimulatory or inhibitory effects of others, suggesting that the search for strong attractants may be furthered by experimenting with combinations of compounds.