APPLE INSECTS — BORERS AND MISCELLANEOUS 201 



time on the softer tissues under the bark, packing its burrow 

 with its sawdust-like castings and gradually })oring towards 

 the base of the twig. As the borer grows it often consumes the 

 larger portion of the Avood and ejects some of its castings 

 through holes made in the bark. Later it bores along the center, 

 making a more or less oval chamber. Early in the fall it eats 

 away nearly all the wood, plugs the end of its burrow and waits 

 for the wind to break off the nearly severed branch. The pur- 

 pose of the grub in this pruning operation is not definitely 

 knowai. Early writers attributed to the grubs an unwarranted 

 degree of intelligence, almost reasoning powers, by which they 

 were considered infallible, knowing just how far to cut and 

 being able to vary the operation to meet the circumstances in 

 each particular case. The most plausible explanation yet sug- 

 gested is that the grub nearly severs the branches and plugs 

 the free end of the burrow to provide for the emergence of the 

 weak-jawed beetles, which could never eat their way out through 

 the solid wood. Under natural conditions in the field the life- 

 cycle of this twig-pruner is doubtless completed in a year, but 

 when infested twigs are gathered and kept in dry situations, it 

 may require three or four years to breed the beetles. 



Oak and maple are favorite food-plants of this insect and 

 the ground is often strewn with severed branches under these 

 trees. It attacks many other forest or shade trees and shrubs, 

 and the following fruits are also pruned by it, sometimes quite 

 severely : apple, pear, quince, peach, plum, grape and orange. 



Several birds, woodpeckers, blue jays and chickadees destroy 

 many of the grubs or pupae in the fallen twigs. A parasite, 

 Bracon eurygaster, has been reared from infested twigs. 



The collection and burning of the fallen branches in autumn 

 or early spring will effectually control the pest. 



Reference 

 U. S. Bur. Ent. Cire. 130. 1910. 



