Invasive Species Compendium

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Abstract

The Biology of Canadian Barkbeetles. The seasonal History of Dryocoetes confusus Sw.

Abstract

These observations on the life-history of Dryocoetes confusus, Sw., in Abies lasiocarpa were conducted, under cage conditions, in British Columbia during 1929-30. In 1929, the young adults emerged from hibernation during the second half of June and throughout the greater part of July, and attacked fresh trees, in which they excavated first brood tunnels. Egg-laying in these was not completed until well into August, after which both sexes made feeding tunnels in which they passed the winter. The mortality among the eggs was very high, probably owing to the unusually cold wet weather, but about 10 per cent. hatched during the second half of August, and by the 21st of the following June the overwintered young larvae had cut mines up to 25 mm. in length. The first pupa of this brood was observed on 30th July, and by 19th August new adults were to be found. They were still present in the trees on 26th August, and probably remained there until the following spring.
The parent beetles resumed their activities in the spring of 1930. The females at first constructed feeding and later second brood tunnels, in which they again oviposited. By 30th June their newly excavated extensions were up to 25 mm. long and contained from 5 to 14 eggs each. Oviposition continued until the first week in July, after which the adults entered fresh trees, in which third brood tunnels were excavated. Egg-laying in these tunnels was completed by mid-August, and although the parent beetles were still present in them at the end of the season, they probably do not survive a second winter. Larvae from eggs laid in these tunnels were first observed on 16th August, and 10 days later approximately 25 per cent. of them had hatched; in no case, however, were larvae found in tunnels less than 23 days old.