Olfactory Responses of Hylastes Nigrinus (Coleoptera: Scolytidae) to Various Host Materials

Hylastes nigrinus (Mann.) is attracted to, and breeds in, the roots of both cut and beetle-killed Douglas-fir trees; the latter are preferred. The beetles reach the roots by digging through the soil. Bark samples taken from trees of various physiological condition and placed in field olfactometers showed that the beetle prefers the bark of insect-killed trees, although bark taken from healthy Douglas-firs became attractive after some time. Among the various terpenes tested, α-pinene and β-pinene were most attractive, in addition to Douglas-fir resin itself.