22 



THE DISTINCTIVE, VISIBLE EVIDENCES OF THE SPRUCE DESTROYER'S 



WORK. 



The characteristic features which are of considerable importance to 

 the forester and lumberman in recognizing the presence and work of 

 this beetle and its broods may be mentioned, as follows: 



PITCH TUBES. 



The tubes or balls of pitch, which are pushed out from the wounds 

 made by the beetles when excavating an entrance for their galleries 

 constitute one of the first and most characteristic indications of the 

 presence of this pest in the living spruce. If upon cutting into the 

 bark around one of these pitch tubes, injuries are found like those 

 just described (Pis. Ill and IV), one may be quite certain that they 

 are the work of the true spruce destroyer. 



APPEARANCE OF THE LEAVES. 



The leaves of a dying tree infested by this insect change from the 

 dark healthy to a pale or grayish green, and soon fall, thus indicat- 

 ing the presence of this pest. And if the bark of an infested tree is 

 examined at this stage, fully developed larvae and even fully 

 developed broods of the adult may usually be found. 



APPEARANCE OF THE TWIGS. 



After the leaves have fallen the infested trees present, by their 

 reddish appearance, a far more striking contrast with the healthy 

 foliage, and are thus easily recognized at a considerable distance. If 

 the bark is examined at this stage the broods of the spruce destroyer 

 will be found nearly or quite fully developed, or they may have 

 emerged. 



APPEARANCE OF THE BARK AND WOOD. 



Since it is absolutely necessary for the beetle to deposit its eggs in 

 living or partly living bark, in order for the young larv?e to have the 

 proper conditions for their future development, there is seldom more 

 than one set of broods developed in the same tree, unless, as is some- 

 times the case, but one side of the tree is attacked one year and the 

 other side the next, when two sets of broods might develop in the 

 same tree. As a rule, all have emerged before the twigs begin to 

 change from their fresh reddish appearance after the leaves have 

 fallen. After this stage is passed the previous presence of the beetle 

 is indicated only by the evidences of its work in and beneath the bark 

 and on the surface of the wood, which may be readily recognized from 

 the illustrations and descriptions given. (PI. V.) The pitch tubes 

 sometimes remain on the bark several years after the tree dies, and 

 as long as there is any bark on the middle portion of the trunk this 



