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THE WESTERN PINE BARK-BEETLE. 

 (Dendroctonus brevicomis Lee.) 



This is one of the two injurious species concerned. It is a cylindric, hard- 

 shelled beetle, from two to three-sixteenths of an inch in length, and varies 

 in colour from light-brown, when recently transformed, to nearly black whea 

 mature. It is clothed above with very short inconspicuous hairs. The young 

 are small, whitish, footless grubs, with powerful jaws, found boring chiefly in 

 the outer portion of the inner bark. 



Fig. 2. The Western Pine eBark-betle. 



( Dendroctonus brevicomis Lec.J Greatly enlarged. 



(Original.) 



THE LIIE-HISTORY AND HABITS. The beetles enter the green bark of 

 healthy, injured, or recently felled trees in pairs during the summer months, 

 and excavate long, irregularly winding egg-tunnels, mostly upwards from the 

 entrance-hole, through the inner bark, upon the wood-surface. A portion of 

 the red boring-dust and excrement is thrust from the entrance-hole and lodges 

 in the bark crevices below; the remainder blocks the egg-tunnels. When the 

 attack is made upon green trees, the exuding resin forms in irregular masses 

 about the entrance-hole, and drops fall and adhere to the bark below. The 

 male beetle keeps the entrance free through this mass of gum, which is known 

 as the "pitch-tube" or "gum-tube." The presence of these gum-tubes upon 

 the bark of injured trees indicates positively that the tree was attacked while 

 the bark was green and full of fluid resin. 



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