Forest Devastation 49 



These insects are small, nearly cylindrical, hard-shelled 

 beetles from an eighth to a quarter of an inch in length, 

 and of varying colors, from light brown to almost 

 black. They enter the bark of the tree in pairs, each pair 

 boring a tunnel upward through the inner bark or slightly 

 grooving the wood. Some of the dust caused by the boring 

 falls out of the openings and forms a ready means of de- 

 tecting the presence of the insects. The eggs are laid in 

 these tunnels and in a short time hatch into small white 

 grubs, each with a strong pair of jaws. These larvae then 

 bore winding channels along the surface of the wood, each 

 one finally hollowing out a chamber in which it passes into 

 the pupa stage. From this stage it emerges a full-grown 

 beetle, bores a passage to the surface, and escapes to select 

 a mate and begin the process on another tree. The winter 

 is passed in any of the three stages, and the work of de- 

 struction is going on fairly constantly all summer, but 

 more particularly in July, August and September. 



The injury is done by the network of tunnels killing the 

 inner bark of the tree. This inner bark contains the ducts 

 through which food material passes downward from the 

 leaves to all other parts of the tree. The insect tunnels 

 cut these, preventing the passage of the food supply and 

 thus killing the tree. A bad attack has about the same 

 effect as girdling, and will kill it in a single season. 



These beetles are not new insects introduced from an- 

 other country. They are native wherever forests of conifers 

 are found. Under ordinary conditions, however, they 

 prefer the bark of dead or dying timber, and, as the supply 



