122 THE SCOLYTID BEETLES. 



followed by the lateral extension of the larval mines of the young 

 broods, which serves to completely girdle the tree and kill the inner 

 bark, and tins in turn is followed some months later by the gradual 

 or sudden dying of the leaves and the complete death of the tree. 



The trees on winch a successful attack is made in June or Jul}' will 

 have the leaves faded and fallen by October, but the leaves on those 

 attacked in August or later may remain normal until the following 

 May or June before they fall. 



EXTENT OF DEPREDATIONS. 



The evidence we have been able to collect shows that at various 

 times during the past century this beetle has been the cause of the 

 death of an enormous amount of the best matured spruce timber in 

 the forests from New Brunswick to northern Xew York and in places 

 in Canada. It is also evident that it will continue to be a menace to 

 standing matured timber, probably throughout the region in which 

 the red and white spruce prevail in forest growth. 



In a report by C. W. Johnson (1898, pp. 73-74), reference is made 

 to extensive destruction of red spruce in the mountains north of Stull, 

 Wyoming County, Pa,, supposed to have been caused by a Dendroc- 

 tonus identified as D. rufipennis. Specimens collected by Mr. Johnson 

 have been examined by the writer and found to be D. piceaper&a. 

 Mr. Johnson stated that some 5,000,000 feet of spruce had been killed 

 on the lands of one company, apparently during 1896 and 1897. 



EVIDENCES OF ATTACK. 



The first evidence of attack on living trees is reddish boring dust 

 lodged in the loose bark and moss on the trunk and around the base 

 of the tree, or numerous fresh gum spots or pitch tubes mixed with 

 whitish or reddish borings on the bark of the middle or lower portion 

 of the trunk. When this is found it will indicate that the beetles 

 are actively at work excavating the galleries in the bark. After this 

 work is completed and the broods of larvae have killed the inner bark 

 the pitch tubes have an old or dried appearance and the boring dust 

 is less evident. By the time the larvae have developed and trans- 

 formed into pupae and adults during September and October the 

 infested trees are indicated by the faded pale-green appearance of the 

 needles on the trees or on the ground, and by the reddish appearance 

 of the tops from which the needles have recently fallen. During the 

 winter and following spring the trees that were attacked later in the 

 preceding summer will present the same evidence of infestation, and 

 in addition a large percentage of the infested trees are usually marked 

 by woodpecker work. The birds discover the broods of beetles and 

 larvae, and in their efforts to get the insects they remove a sufficient 

 amount of the outer loose bark to give the trunks a conspicuously 



