Response ofScolytus multistriatus (Coleoptera: Scolytidae) to α- and δ-multistriatin in Switzerland.

Laboratory bioassays and field tests demonstrated that a Swiss population ofS. multistriatus responded much more strongly to α- than to δ-miltistriatin in combination with 4-methyl-3-heptanol and α-cubebene. High concentrations of brevicomin appeared to replace α-multistriatin in evoking a response byScolytus species, but this effect can be explained by the fact that the brevicomin was contiminated with small amounts of α-multistriatin. Frontalin, another bicyclic ketal, showed no biological activity. Field tests indicated thatS. pygmaeus aggregates to the same attractant mixture asS. multistriatus. S. scolytus also responded preferentially to this mixture, but the relative amounts of α-multistriatin to 4-methyl-3-heptanol do not appear to be as important as forS. multistriatus.

Responses of the olfactory receptors ofScolytus scolytus (F.) (Coleoptera: Scolytidae) to the stereoisomers of 4-methyl-3-heptanol.

Electroantennogram (EAG) and single-cell recording techniques have been used to demonstrate the presence of separate receptors for (-)-threo- and (-)-erythro-4-methyl-3-heptanol on the antenna ofS. scolytus. The majority of single-cell recordings showed spikes of two different amplitudes. The cell giving spikes of larger amplitude responded to the (-)-threo stereoisomer while the cell with the small-amplitude spikes responded to (-)-erythro-4-methyl-3-heptanol. It is suggested that in most recordings the two cells are associated with a single sensillum basiconicum.