THE BIOLOGY OF IPS PERTURBATUS EICHHOFF

Abstract

The biology of Ips perturbatus in the Gaspé Peninsula is described from observations made during the summer of 1933 and 1934. This species generally breeds on trees killed by Dendroctonus piceaperda Hopk. but was also found on white spruce dying from the attacks of Diprion polytomum Hartig. In the Gaspé peninsula there is one complete generation a year. At the end of September and the beginning of October, the young adults leave their host tree to hibernate in the ground. Emergence from the ground occurs in the spring.Experiments show that the adult stage lasts nearly two years. During their first complete summer as adults, the females lay two sets of eggs. The following spring they lay a third set and die during the summer. There are one to four egg tunnels per engraving. The average number of eggs per egg tunnel decreases with the increase in the number of females per engraving. Dissection of 500 beetles indicates that the two sexes are present in about equal proportions. Analysis of the results of a population study made on a white spruce representing 48 feet of tree superficies attacked by Ips perturbatus produced the following results: 2448 egg tunnels, 22,512 young beetles, 58,800 egg niches and a mortality rate of 58.33%.Coeloides dendroctoni Cushm. is the most important parasite of this species, but does not kill more than 5% of the larvae and pupae. No trace of woodpecker control was noticed.