HO A MANUAL OF FORESTRY 



spruce timber by its borings in the cambium, the living tissue 

 just beneath the bark. Here it makes its primary galleries 

 and lays its eggs. As soon as the eggs hatch the young broods 

 make transverse galleries which effectually girdle the tree, and 

 in time the withering leaves proclaim the death of the tree. 

 The falling leaves are an outward sign of the damage; by remov- 

 ing the bark the galleries made by the insects may be plainly 

 seen. 



Appearance. -The adult is a reddish-brown or black beetle, 

 varying in length from three-sixteenths to one-quarter of an inch. 

 The egg, small and nearly white, is not distinguishable from that 

 of other bark beetles. The larva, at first a minute white grub, 

 becomes about one-quarter inch long. The pupa is nearly white 

 and of about the same size and form as the adult;- it is found in 

 cavities in the bark. 



Life History. Simultaneously a large number of beetles will 

 attack the lower part of a large-sized spruce. Trees over ten 

 inches in diameter may be attacked. They bore through the 

 bark and deposit their eggs in the galleries as already described. 

 The eggs soon hatch and each larva bores its individual gallery 

 where it matures. The period of development from egg to 

 mature larva varies according to the season, from two to nine 

 months, but the adult seldom develops sufficiently to emerge 

 until another spring. The result is, when activity ceases in 

 October, that a tree may contain the insect in all its stages of 

 growth. 



Treatment. Nothing can be done to save a tree once in- 

 fested with this borer, but much can be done to prevent the 

 spread to other trees. Theoretically the best method is to make 

 trap trees by hack girdling them in May or June. The beetles 

 are thus led to concentrate on these weakened trees, and these 

 are to be destroyed in the fall, winter or early spring, either by 

 the removal of the timber from the forest or by felling and 

 removing the bark before the insects emerge. Intelligent lum- 

 bering of the areas of infected trees, and of all mature trees, is 

 the most practicable way of keeping this insect in check. 



