THE SPRUCE INVESTIGATION. 259 



of them entering the wood only when they have attained their 

 full growth, while others enter as soon as they have attained 

 sufficient size and strength to do so. 



Large numbers of apparently different kinds of round-headed 

 wood mining larvae, were found in the spruce, but only a few 

 species could be identified, owing to the fact that the adults 

 could not be bred. 



The Destructive Spruce Wood Miner 1 deserved special atten- 

 tion, since it is the one which contributes to the rapid decay of 

 the wood of standing trees, and since the young grub has been 

 found mining in the living bark on living trees, it might easily 

 contribute to the death of some trees. The trouble caused by 

 this insect is described at length in another part of this report. 

 It is therefore only necessary to state that it is a common in- 

 sect throughout the spruce area, to which it is probably con- 

 fined in its distribution in West Virginia. 



The eggs are deposited early in the spring, by a slender, light- 

 brown beetle in the outer bark on the trunk of large trees, us- 

 ually at points from near the base to the first branches. These 

 eggs hatch into minute, white worms, which mine through the 

 inner bark ana outer surface of the wood, until they are nearly 

 full grown, when they enter the sapwood in which they mine 

 until they have attained their full size, which is from 7 twelfths 

 to 8 twelfths of an inch in length and an average width of about 

 3 twelfths inches. The three front segments are slightly broader 

 than the others, and each is provided on the underside with a 

 pair of small legs. Each example of the matured larvae exca- 

 vates a cavity in the wood, and also an exit gallery 

 to the outer bark. The mouth of the inner cavity 

 or pupa case is then packed with borings and the larva trans- 

 forms to the pupa and adult within the cavity, after which 

 the beetle finds its way out through the exit prepared by the 

 larva. 



INJURY TO TERMINAL BRANCHES BY THE WHITE PINE WEEVIL, 2 



This insect which has been mentioned by other writers as 



1 Tetropium cinnamopterum, Kirby. 



2 Pissodes strobi, Peck. 



