WEST VIRGINIA GEOLOGICAL SURVEY. 



89 



structive insects that injure our different classes of forest trees 

 and forest products. 



Insects That Attack the Bark of Living Trees. 



Among the most serious enemies of coniferous forests are 

 the different species of beetles that in their adult and larval 

 stages attack the inner bark of living trees excavating galleries 

 for the reception of their eggs and for food. Beetles of this 

 class belonging to the genus Dendrotonus have been notably 

 destructive in West Virginia and in many sections of this and 

 other countries, the genus being represented at present by 23 

 North American and one European species. The beetles of the 

 different species are somewhat variable in size, ranging from 2 

 to 7 mm. in length. The color is brown, reddish-brown or 

 black. The beetles have broad heads and the general form of 

 the body is elongate, cylindrical and stout. 



The beetles mine in the bark of their host trees for a dis- 

 tance of a foot or more and construct egg galleries. The larvae 

 hatching from the eggs destroy the bark intervening between 

 the burrows and galleries made by the adults thus girdling the 

 trees and causing their speedy death. 



As a result of conditions that favor their multiplication 

 these beetles sometimes appear in swarms and attack lining 

 healthy trees over wide areas of country. Hopkins estimates 

 that if the timber destroyed in the United States by this one 

 group of insects during the past fifty years were living today 

 its stumpage value would exceed $1,000,000,000. 



In 1891 and 1892 the southern pine beetle, {Dendroctonus 

 frontalis (Zimm) appeared in the spruce and pine regions of 

 West Virginia and Virginia, and, to a less entent, in North 

 Carolina, the District of Columbia, Maryland and Pennsyl- 

 vania and killed a very large percentage of young and old 

 trees on an area of over 75,000 square miles. The loss in West 

 Virginia from this outbreak was great as nearly all the pine 

 and spruce trees in thousands of acres of fine forest were killed 

 while shade and ornamental pine trees within the infested areas 

 suffered the same as those in the forests. In the Potomac basin 



