268 INSECTS 



the solid wood only to pupate. Some of the round- 

 headed borers have similar habits but on the whole 

 they are more diverse in their methods of feeding than 

 the flat-headed borers. With both we have species 

 that attack only dead or dying tissue, and others that 

 will feed in or on perfectly healthy trees. Some of them 

 must have matters just exactly right, like the twig- 

 girdler which lays an egg and then girdles the twig 

 below the point of oviposition, so that in the first high 

 wind it may break off and fall to the ground. Others 

 like the oak-pruner demand living wood as food for 

 the larva, but a dead twig for pupation; so the larva 

 girdles the twig from the inside, leaving only a thin 

 shell, makes itself comfortable beyond this point, and 

 waits the time when it is blown to the ground to com- 

 plete its transformations. 



Another important series contains the bark beetles 

 which, while they do not so much affect the horticul- 

 turist, do most seriously affect the forester and the 

 lumberman. It would hardly pay to go at much 

 greater length into the different kinds of borers, be- 

 cause the fact of general infestation has been suffi- 

 ciently brought out. 



We see from this brief review that from the time the 

 plants first show above ground until the harvest is in, 

 they are subject to the attacks of sucking and chewing 

 insects in all their parts, and that neither root, stem, 

 leaf, fruit nor seed is free from liability to infestation 

 and injury. Some of this liability is increased by inju- 

 dicious farm practice, some of it is the consequence of 

 past carelessness, and a portion is due to the inevitable 

 change in the balance of nature caused by culture and 

 by planting large areas in one sort of vegetation. 



It follows that the agriculturist and horticulturist 

 is always at war with insects, either actively or pas- 



