92 THE DESTRUCTIVE AGENTS OF FORESTS. 



known as carpenter moths. Injuries of this kind are common 

 in the oaks of West Virginia. 



Another class of defects which are somewhat distinct in 

 appearance are the ''grease spots" or "black holes" found in 

 white oak, chestnut oak, beech, yellow poplar and other species 

 of trees. These are caused by one of the so-called ambrosia 

 beetles {Gorthylus columhianus Hopk.) These defects are very 

 abundant and are the cause of much loss especially in hard- 

 woods. 



The Locust Borer {Gyllene robinae Forst.) is a destruc- 

 tive enemy of yellow locust in West Virginia. Some sections 

 of the state are comparatively exempt from the ravages of this 

 species while in other sections injuries done are so great that it 

 is almost useless to attempt to grow locust trees. Hopkins 

 states that the locust timber on the Potomac waters is compar- 

 atively free from these insects but that they are plentiful on 

 the Greenbrier river. They are abundant also in the central 

 and western parts of the state and about Morgantown. 



The adult locust borer is a very handsome yellow and 

 black beetle that deposits its eggs on the bark of the host tree 

 in the fall. At this season the beetles may be found also fre- 

 quenting the blossoms of goldenrod. The larvae feed first in 

 the bark and later extend their burrows into the solid wood. 

 Their presence is always indicated by the sawdust-like borings 

 which the larvae eject from their burrows. 



Dying and dead pine wood is also attacked by ambrosia 

 beetles and the sapwood seriously injured by the pinholes 

 which the insects make. A fungous growth develops in these 

 pinholes which stains the wood and hastens decay. Hardwood 

 trees when about to die and when dead are attacked by a great 

 variety of insects the most destructive of which are the round- 

 headed borers, timber worms and ambrosia beetles. The 

 promptness with which many of these insects enter the trees 

 after they are killed and the rapidity with which they extend 

 their burrows in every direction through the wood makes it 

 important that trees killed by any agency should be manufac- 

 tured as soon as possible after their death in order to sustain 

 the minimum of loss. 



