INSECTS AFFECTING PARK AND WOODLAND TREES 



379 



after the attack has practically ended. It will be observed that the inner 

 bark is a mass of partially decayed tissues tunnelled b)' numerous larval and 

 adult galleries. Figures 82, 84 represent the condition after the decayed 

 tissues have been removed. The adult galleries may be easily recognized 

 where they score the surface of the wood and here ant! there are peculiar 

 chambers a little to one side of an adult gallery. These are not central or 

 entrance chambers but are evidently Httle cavities hollowed out by the 

 beetles for the reception of balsam and show conclusively that the tree must 

 have been alive at the time of the initial attack. The hard, dried balsam 

 can easily be found in such cavities. 



Figure 83 illustrates very nicely how thorough!)' this insect may girdle 

 twigs. It represents a small twig less than y^, inch in diameter and shows 

 the adult galleries of two females passing from a central chamber around 

 the twig in opposite directions and overlapping each other on the farther 

 side by about ],{ inch. 



The larvae or grubs pursue a rather tortuous course at approximately 

 right angles to the parental galleries and end their operations in a slightly 

 enlarged elliptic cell where the final transformations to the beetle occur 



Natural enemies. The writer collected two parasites, S p a t h i u s 



t o m i c i Ashm., and C o s m o p h o r u s h o p k i n s i i Ashm. in the burrows 



of this bark borer. 



Bibliography 



1903 Felt, E. P. For. Fish & Game Com 7th Rep't, j). 519-22 



Spruce destroying beetle 



Dendroctoniis piccapercia Hopk. 



A rather stout, brownish or black beetle about 3 ,6 inch long, makes longitudinal 



galleries in the inner bark and outer sapwood of living spruce. These, in connection with 



the mere or less transverse expanding larval galleries, frequently result in the destruction 



of trees. 



This species, though only recently characterized, is an exceedingly 

 destructive form, and its ravages have been known for some years, though 

 the operations were usually attributed to another species. 



