BORING INSECTS 55 



borers. The bark borers are most dangerous; 

 the wood borers are perhaps most widely distrib- 

 uted. 



The insects which do harm to the inner bark 

 and outer sapwood belong (as do most of the 

 heartwood borers) to the order Coleoptera, or 

 beetles, distinguished by their hard " sheath- 

 wings " covering the pair which are used in flight. 



First among the beetles come the weevils, or 

 snouted beetles, a race which devotes its attention 

 most largely to fruits and stored nuts and grains. 

 Half-a-dozen representatives live in the bark of 

 trees. The cypress weevil mines in the bark of 

 injured bald cypress, and the walnut weevil is at 

 home in the Inner bark of dying walnut trees. 



Much more destructive are the bark beetles, or 

 " shot-hole borers " as they are often called, in 

 reference to the little round black-edged holes 

 which they make as exits from the tree. Most 

 of them make beautiful seaweed-like markings up- 

 on the surface of the wood, just beneath the bark. 

 The most notorious member of the family is the 

 hickory bark beetle, a stumpy, shining black or 

 reddish-brown citizen, hardly more than an eighth 

 of an inch long. The adults are common during 

 the summer, feeding on hickory twigs. The eggs 

 are laid in the limbs or upper trunk of the tree. 

 The insect excavates a vertical tunnel an inch or 



