Pheromone receptor cell specificity in interpopulational hybrids ofIps pini (Coleoptera: Scolytidae)

Electrophysiological studies of pheromone receptor cells keyed to ispdienol were performed in laboratory-raised hybrids of the eastern and western populations of the pine engraver,Ips pini. As previously shown in the parental beetles, the receptor cells keyed to ipsdienol could be classified as two distinct types: one keyed to (+)- and one to (–)-ipsdienol. None of the 20 ipsdienol cells recorded from F₁ hybrids were of an intermediate type. Recordings of the summated receptor responses (EAGs) showed no significant difference between parental beetles and hybrids. Similar results were obtained in reciprocal crosses, eastern females with western males and the reverse. Thus, there was no indication that sex-linked alleles determined the specificity of the ipsdienol receptor cell. The ratio between (+) and (–) cells was 146 in the hybrids compared to 112 in the western and 912 in the eastern populations.