BARK BEETLE OLFACTION. III. ANTENNAL OLFACTORY RESPONSIVENESS OF Dendroctonus frontalis Zimmerman AND D. brevicomis Le Conte (COLEOPTERA: SCOLYTIDAE) TO AGGREGATION PHEROMONES AND HOST TREE TERPENE HYDROCARBONS

Electroantennograms from males and females of Dendroctomts frontons and D. brevicomis in response to serial dilutions of the pheromones exo brevicomin and frontalin and the host terpene hydrocarbons 3-carene and a-pinene show no significant differences in the threshold concentration for response to the compounds for either sex or species. The intensity of response was greater to higher concentrations of the pheromones (10 to >10(4) mu g) than the terpene hydrocarbons, suggesting the presence of more receptors on the antennae for pheromones than terpene hydrocarbons. Antennal olfactory responses to the compounds did not correlate to published data on behavioral responses by the beetles to the compounds in both field and laboratory studies. Adaptation experiments indicated that for D. frontons, both frontalin and exo brevicomin share the same receptors on the antennae. The results indicated that the terpene hydrocarbons share some, but not all, of the same receptors.