256 THE CANADIAN ENTOMOLOGI^T. 



majority of species attack only dying or dead trees.* Stumps, diseased or 

 dead branches, brush piles and recently-felled logs are their favourite 

 breeding places. Most species will not, as a rule, molest living trees at 

 all if rapidly-dying and recentiy-fclled food-plants are available, but if trees 

 in this condition are not to be had in sufficient quantity, many of these 

 species will attack perfectly healthy trees and prove very destructive. 

 Between 1882 and 1889 Po/ygraJ'/ius ru^pennis, which does not ordinanly 

 feed upon living trees, destroyed, according to Dr. Hopkins, approximately 

 10% of the 500,000 acres of growing spruce in West Virginia. 



The injury done by the species which attack healthy and diseased trees 

 is, in certain regions and at recurring intervals, very considerable. The 

 work of Dendroctoims frontalis in the spruce and pine of West Virginia and 

 the adjoining States, oi D. piceaperda in the spruce of the Northeast, and 

 o{ D. ponderosa in the spruce and pine of the Black Hills of South Dakota, 

 may be cited in illustration. D. frontalis and D. ponderosa attack the 

 living, healthy spruce and pine, and in spite of the resin are able success- 

 fully to rear their young within the bark. The tunnels and mines thus 



formed interfere seriously with the flow of sap, and either kill the tree 

 outright or induce an unhealthy condition favourable to the attacks of 

 other borers and fungous diseases. It seems very probable that many 

 destructive forest fires have been i&d by trees dying or dead from the 

 attacks of Scolytids. In 1903 Dr. Hopkins estimated that the destruction, 

 in the previous three or four years, of 10% of the white pine and 75% of 

 all other species of pine, throughout an area of over 10,000 square miles 

 in the Stales of Virginia and West Virginia, was to be attributed 

 to the ravages oi D. frontalis. In 1904 the same writer pointed out that 

 D. ponderosa had been the primary cause of the destruction of 

 1,000,000,000 feet of Bull Pine in the Black Hills of South Dakota and 

 the Rocky Mountain region. 



The Timber-beetles, by driving their tunnels through the wood in 

 many directions, often render timber unfit for use. 



Hylastinus obscurus breeds in the roots of clover in many parts of 

 the Northeastern States and in Canada, and in some localities proves a 

 serious pest. 



Cort/iylus pjiuctatissimus occasionally does considerable damage in 

 young sugar-maple plantations. 



Scolytus rugulosus, the fruit bark-beetle, attacks unhealthy fruit trees 

 of all sorts, and occasionally bores in apparently perfectly healthy trees. 



Phloiotribus liminaris frequently attacks diseased peach and cherry. 



Xyleborus dispar sometimes occurs in diseased apple trees. 



*(A few breed in dead wood only.) 



iMailed July Sth, 190; 



