94 



THE SCOLYTID BEETLES. 



and adults in individual cells at the farther end or toward the 

 middle of their larval mines, which are exposed in the inner bark 

 when it is removed from the tree. Both the egg galleries and larval 

 mines cause marks and grooves on the surface of the wood. After 

 the new broods of adults become matured, they burrow through the 

 intervening bark between their cells, and congregate in the general 



Fig. 54.— The Black Hills beetle: Galleries in bark and marked on scoring chip. 

 • natural size. (Author's illustration.) 



About one-third 



cavity thus formed, until the proper time for them to emerge, when 

 they all come out and fly in swarms to attack the remaining living 

 timber. 



Sufficient information relating to the flight of this species has 

 been secured to indicate quite conclusively that it flies in swarms 

 during the day, and probably at night. 



