118 FIRST P.O(^K OF FORESTRY 



The mischief done by forest insects is very varied. The 

 bark beetles kiU nearly all kinds of trees ]:>y a queer process 

 of gu'dling ; the moths operate through their larvae, the 

 caterpillars, and usually kill by eating the leaves and 

 buds ; the weevils destroy young plants ; the pruner beetles 

 injure by gnawing off the young tips ; gall gnats and 

 plant lice do damage by the production of galls ; scale 

 insects suck the juice, and thereby cripple the leaves and 

 injure the bark ; while the mole cricket and other insects 

 gnaw young roots, and thereby often destroy the smaller 

 plants. But even after the tree is dead its wood is still 

 liable to be spoiled for most uses by some long-homed 

 beetles and their larva?, the " sawyers," as well as the 

 regular timber beetles. Of all these the bark beetles and 

 moths with their larvae, the grubs, and caterpillars, are 

 by far the worst enemies of the forest. 



Let us examine these more closely. In Fig. 46 we 

 have the bark beetle and its work. In the spring these 

 tiny beetles fly, usually in pairs, and hunt up some suitable 

 tree. After they have found what they want, usually 

 some large, old or injured tree, they bore through the 

 bark, and the female soon begins to bore a passage or 

 gallery, either altogether in the soft bark or else partly in 

 the bark and parti}' in the wood, as shown in the figure. 



Along this passage she lays from fifty to a hundred 

 eggs, distributing them along both sides. When the 

 eggs hatch the little grubs Ijegin to bore in the direction 



