Insect Damage 49 
especially of coniferous trees, and feed on the soft cambium 
layer, are usually secondary troubles, after the vigor of the 
tree has been undermined by defoliation, by fire, or by other 
causes. They rarely attack vigorous and healthy trees; 
sometimes, however, when a pest is excessively abundant, 
healthy trees may be attacked and succumb, especially 
young specimens. Since the larve of these beetles destroy 
the cambium, their damage becomes easily very serious, 
leading to the death of the tree. And as their presence is 
not readily detected before the mischief is done they are 
most difficult to deal with. 
Not less insidious and difficult to combat are the wood- 
borers and wood-wasps which burrow in the wood, or hollow 
out the pith of twigs. Although they are mostly less injuri- 
ous to the tree, being usually few in number and working 
as they do in dead wood, yet when they attack the smaller 
branches and young trees they may cause undesirable loss. 
Even in the bole of older trees they may, if very numerous, 
undermine the vitality of the tree by reducing the conducting 
tissue so as to eventually cause the death of the less vigor- 
ous individuals. Moreover, these boring insects may pro- 
duce mechanical injuries which furnish an entrance for 
fungus growth and thereby lead to more serious trouble. 
The roots suffer also from a number of insects. Some of 
them destroy the youngest root tips mechanically, as is done 
by the mole-cricket and the larva of the June bug, while wire- 
worms and other beetle larve, and a few caterpillars and 
root-lice living underground, feed on them, and others again 
burrow in them. The damage is usually of moment only 
in young trees and is, of course to be found in the loss of 
feeding apparatus. 
There should perhaps here be added, since the question 
occasionally arises, a few remarks on “how to kill a tree.” 
