OLFACTORY RECEPTOR CELL RESPONSES OF IPS-GRANDICOLLIS (EICHHOFF) (COLEOPTERA, SCOLYTIDAE) TO INTRASPECIFIC AND INTERSPECIFIC BEHAVIORAL CHEMICALS

Electrophysiological recordings from antennal olfactory receptor cells were obtained from Ips grandicollis. Recordings were made from olfact ory receptor cells from nine regions of the antennae in response to st imulation with the semiochemicals alpha-pinene, frontalin, endo-brevic omin, verbenone, trans-verbenol, cis-verbenol, ipsdienol, and ipsenol. In many cases, up to two cells were recorded concurrently from the sa me location. When compared to males, females had a greater percentage of cells responsive to the primary pheromones of Dendroctonus frontali s, frontalin and trans-verbenol, and of Ips spp., ipsdienol and ipseno l. Among females, more cells responded to trans-verbenol and the Ips-p roduced volatiles than to host or other D. frontalis-produced compound s. Olfactory cells of males responded mostly to cis-verbenol, followed by alpha-pinene, verbenone, trans-verbenol, and endo-brevicomin. Of t hose cells responsive primarily to one compound, the greatest percenta ge were responsive to trans-verbenol in females and to verbenone in ma les. The response of the antennal olfactory receptor cells to semioche micals used by male and female I. grandicollis is consistent with the presence of these compounds during the host colonization period for ea ch sex. Our results, which show a lack of specificity in most pheromon e and host odor receptor cells, is in contrast with previously publish ed accounts of olfactory receptor cell specificity in other Ips specie s.