. Forest insect conditions in British Columbia [microform] : a preliminary survey. Insect pests; Arbres; Forest insects; Insectes nuisibles; Insectes forestiers; Trees. 15 The eggs arc deposited singly in flhalluw niches cut by the female along the sides of the egg-tunnel at intervals of a half-inch or more; and the young larvte, or grubs, which hatch in about eight days, bore irregularly, mainly in the outer layers of the inner bark. When nearly full-grown the grubs bore outwards deep into the middle layers of bark, enlarge the ends of the tunnels to form pupal-cells," and there transfor
. Forest insect conditions in British Columbia [microform] : a preliminary survey. Insect pests; Arbres; Forest insects; Insectes nuisibles; Insectes forestiers; Trees. 15 The eggs arc deposited singly in flhalluw niches cut by the female along the sides of the egg-tunnel at intervals of a half-inch or more; and the young larvte, or grubs, which hatch in about eight days, bore irregularly, mainly in the outer layers of the inner bark. When nearly full-grown the grubs bore outwards deep into the middle layers of bark, enlarge the ends of the tunnels to form pupal-cells," and there transform to the resting-stage or pupa. The adult beetles, which appear later from the pupce, bore round holes through the outer bark and escape to spread the infestation to green trees, or to increase the numbers ir ?he trees already Fig. 4.—Larva or grub of the Western White Pine Barli- bectle. Greatly enlarged. (Original). Many yf the beetles attack the trees near the red-tops from which they escape: but swarms, spreading from the old infestations, attack isolated trees and small clumps of trees at a considerable distance. The outbreak thus spreads by the increase in the number of the clumps and scattered infested trees, as well as by the enlargement of the individual clumps. The Seasonal History of the Broods.—There are, at least about Prince- ton, one brood and a partial second one each season. During .he winter there may be found in the bark: the parent adults of the fall brood; young, light- coloured adults still in the pupal-cells; and many larvae, or grubs in various stages. The ovor-wintered parent adults extend their tunnels, or start new ones, when the weather becomes warm in spring, and deposit eggs. The adults developeil from these eggs appear, apparently, early in August and start tunnels in the trees already attacked by the broods of over-wintered young adults. At Princeton this year these over-wintered parent adults largely left the bark and started new
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