Bark Beetle Attractants: Trans-verbenol isolated from Dendroctonus

Abstract

MASS aggregations of populations of Dendroctonus (Scolytidae) on new host trees are largely caused by olfactory responses to attractants created by the attacking females^1,2. The attractant is apparently composed of host and insect components which interact in some unknown manner in orienting the population to new hosts. In our experiments with Dendroctonus brevicomis Lec. in California, D. ponderosae Hopk. in Idaho, and D. frontalis Zimm. in Texas, mass aggregation could not be induced by either host or insect factors when tested independently. These results are contrasted with those obtained with another group of scolytids (certain Ips) where faecal matter per se from mature males was highly attractive^3,4. In both groups of bark beetles, however, the mechanism of pheromone release is defaecation and the probable sites of elaboration and concentration are the Malpighian tubes and hindgut area^5,6.