INSECTS AFFECTING FOREST TREES. 



513 



Insects Affecting tl)e 3prace. 



Tlie spruce is one of the valuable timber trees of the Adirondack region, and 

 like the pine is subject to attacks by a number of insects. A few of the more 

 important are noticed briefly here. 



INSECTS ATTACKING THE TRUNK. The trunk of this tree is the home of 

 several species of economic importance. 



Bark Borers. At least one of the members of this cjroup must be considered 

 as a serious enemy of this valuable tree. 



DESTRUCTIVE SPRUCE BARK BORER. 



Polygraplius rufipcnnis Kirby. 



The adult insect is a light brown or black, rather stout beetle, about Yz^ "-"f 3^" 

 inch in length. It may be commonly found running somewhat irregular transverse 

 galleries in the inner bark of the spruce. Eggs are deposited along the sides of 

 the primary galleries and the young grubs extend their mines at approximately 

 right angles and nearly parallel with the bark fibers. This is a very common species 

 in the Adirondacks and must be regarded as a .dangerous enemy of the spruce,, 

 since it is always present in small numbers in cut logs and trimmings. This of itself 

 is not harmful, but when the insect becomes unusually abundant, it may turn its 

 attention from the dead and dying and attack living trees. This borer was observed 

 by the writer associated with species of Dryococtcs in spruce and -with Toinicus 

 balsajiiciis Lee, in balsam. 



/,//(• History. The life history of this borer, as recorded by Dr. Hopkins in 

 West Virginia, is as follows : The adults emerge in May or June and are attracted to 

 stumps, trunks and tops of recently fallen trees and to those 

 weakened by the attacks of insects. The beetles commence 

 to excavate an entrance through the bark and their presence 

 is indicated by the fine brownish borings in the crevices. 

 The entrance is extended to the upper surface of the soft 

 inner bark where the central chamber is excavated. The 

 female, which appears to do most of the work, is now 

 joined by a male which stations himself in the outer gallery 

 to keep out enemies and objectionable visitors, and renders 

 assistance in expelling the borings. The female excavates 

 the galKny from the inner bark to the wood antl then in the inner layer of the bark 

 and at right angles to the bark fibers for a distance of i or 2 inches. Eggs are 



FR;. i_5. Ii'i.) l,l<A/iiL'S 

 RUFIPENNIS. 



EAKLV GALLERIES AND EGG NOTC^IES. 

 ORIGINAL. 



II 



