74 



The Pine Beetle. 



and in a month or so they pupate, that is, form chrysalids, in the 

 bark. A week or two later the chrysalids change into beetles, 

 which eat their way out to the surface. As it generally happens 

 that a very large number of beetles breed in the same tree, the 

 surface of the bark after the young beetles have emerged looks 

 as though a charge of No. 6 shot had been fired into it. 



So far as dead or dying trees are concerned, the action of the 

 insect up to this point is not of serious economic importance. 

 So long as it can get such trees in which to breed, it will not 

 attack healthy trees, but should suitable breeding material not 

 be present, it may make its breeding galleries in comparatively 

 sound stems, which will soon be seriously crippled, or killed 

 outright. 



The young beetles generally appear in June, and they may do 

 one or other of two things. They may either fly off to other 

 pine stems that have been felled or have been dead for a few 

 months, in which case they pair and breed just like their parents. 

 In such an event we have what is called a double generation, 

 that is, two broods in a single season. But more frequently the 



FIG. 3 — PINE SHOOT WITH SLICE REMOVED TO SHEW PASSAGE MADE BY 



THE BEETLE. 



young beetles do not breed in the year in which they are hatched. 

 In this case they fly singly to the young shoots of the Scots or 

 other pine, and into such shoots they bore, usually two inches 



