Behavior of the western pine beetle during host colonization.

After living ponderosa pines were baited with either female-infested bolts or synthetic pheromones,Dendroctonus brevicomis were caught on sticky screens throughout trapping periods of 15-46 days; however, large numbers of beetles were trapped during only a small portion (5-10 days) of these trapping periods. The most attractive portions of trees attacked contained 3-6 beetles dm(2), in galleries ca. 2 cm long. Catch increased following addition of males to female-infested bolts, supporting the hypothesis that male-produced frontalin is an attractive pheromone of the western pine beetle. Catch at bolts removed from trees under attack was strongly dependent upon levels of boring activity. We found no evidence of interruption of the response to attractants during host colonization.