Attraction of Yellowjackets (Vespulaspp.) to Heptyl Butyrate in Washington State (Hymenoptera: Vespidae)

During 2 years of trapping with artificial attractants in the Pullman, Washington, area, 6 species of Vespula were collected. Two species, V. atropilosa (Sladen) and V. pensylvanica (Saussure), were collected in large numbers. V. atropilosa was more strongly attracted to heptyl butyrate than was V. pensylvanica. Most queens and workers collected in attractant traps were V. atropilosa. Use of artificial attractant traps for controlling yellowjackets is discussed in relation to species composition. The importance of appropriate timing is emphasized and related to the seasonal buildup and decline of worker yellowjacket populations.