Bark Beetle Aggregation : Effects of Feeding on the Release of Pheromones in Dendroctonus and Ips

AGGREGATION of destructive populations of Dendroctonus and Ips in pine forests consists of three phases: first, detection and selection of suitable host trees; second, mass attack and colonization; and third, a possible mass attack of adjacent trees. Host finding is believed to be random or guided by host odours. The mass attack of selected trees is caused by attractants or pheromones generated by the insects, and which are effective over considerable distances. The attractants are produced by the host-selecting sex, and released only in contact with fresh host material. The attractive components originating from male Ips and female Dendroctonus are concentrated n the hindgut area and discharged by defaecation 1–4 .