INJURIES BY ROUND HEADED BORERS. 



345 



s 



The-grub (fig. 20, c) is elongate and somewhat cylindrical, yellowish 

 white in color, and about 1 inch long when full grown. Its mouth- 

 parts are dark brown to black, and the under side of the body is pro- 

 vided with three pairs of minute legs. It lives in the bark about a 

 year, emerging in the spring or summer as an elongate, brownish 

 to black beetle (iig. 

 20, ?>), the surface of 

 the body having a 

 velvety appearance. 

 The beetle ranges in 

 length from 9 to 19 

 mm. 1 The principal 

 time of emergence is 

 May and June. This 

 species attacks either 

 healthy, injured, or 

 felled trees. 



The methods of 

 control are preven- 

 tive. Once a tree is <^c 

 badly infested noth- 

 ing can be done to 

 save that particular 

 tree. Something can 

 be done, however, to 

 stop the spread of 

 the infestation to 

 other trees. Infested 

 trees should be felled 

 and barked and the 

 bark burned before 

 May 15. Something 

 could also be accom- 

 plished by the use of 

 trap trees. As the 

 insect breeds readily 

 in felled trees, a few 

 healthy trees felled in May or June near those infested would attract 

 the beetles which would otherwise deposit their eggs in healthy trees. 

 Later in the season, or before the following spring, the bark should 

 be stripped off the trap trees and burned. 



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a 



FIG. 20. Work of the western larch bark-borer (Tetropium 

 velutinum). Section of bark of western larch: a,, Com- 

 pleted larval mines in inner bark ; b, adult beetle ; c, 

 larva ; d, pupa. Insects approximately natural size. 

 (Original.) 



1 1 mm. =5*5 inch. 



