D 



IMPORTANT NORTH AMERICAN FOREST INSECTS O 



THE BLACK HILLS BEETLE 



Dendroctonus ponderosae Hopk. 



The Black Hills beetle is the most destructive enemy of yellow 

 pine in the Rocky Mountain region. It has a marked tendency to 

 increase suddenly to extraordinary numbers and, after destroying 

 great quantities of timber, to subside quickly. Notable epidemics 

 occurred in the Black Hills from 1898 to 1905 and in the Kaibab 

 National Forest from 1920 to 1925 {42). 



THE DOUGLAS FIB BEETLE 



Dendroctonus pseudotsugae Hopk. 



The Douglas fir beetle is most destructive in the northern Rockies 

 and Canada. It seldom kills Douglas fir west of the Cascade Range. 

 Outbreaks are local and sporadic, frequently associated with wind- 

 throws, defoliations, or logging operations {Jfi). 



THE WESTERN PINE BEETLE 



Dendroctonus brevicomis Lee. 



The western pine beetle occurs over practically the same territory 

 as the mountain pine beetle and extends to the southern limit of the 

 yellow pine type in California, This species rarely causes spectacu- 

 lar outbreaks but takes an annual toll of from 0.1 per cent to oc- 

 casionally 5 per cent of the stand. It is of economic importance 

 only in the western yellow pine forests (42, 46). 



THE SOUTHWESTERN PINE BEETLE 



Dendroctonus barber i Hopk. 



In habits this species resembles its near kin, the western pine 

 beetle, though it is not so destructive. Occasional outbreaks in 

 southern Colorado, Arizona, and Xew Mexico take a considerable 

 toll of timber but are short-lived. The activities of the beetle in- 

 crease in years of drought (.££). 



THE JEFFREY PINE BEETLE 



Dendroctonus Jeffrey i Hopk. 



The Jeffrey pine beetle restricts its activities entirely to the tree for 

 which it is named. It is most injurious in the forests east of the 

 Sierras, where it normally takes a small annual toll. Following a 

 severe windstorm in the Inyo Xational Forest, Calif., some 6.000.000 

 feet of timber were killed by this species in 1924 and 1925 (4#, 46). 



THE ENGRAVER BEETLES 



Ips spp. 



The engraver beetles of the genus Ips are represented by numerous 

 species. They are usually associated with dying or recently felled 

 softwoods. Occasionally they contribute to the death of timber 

 weakened from other causes and may even kill outright healthy 

 timber when they are present in great numbers. Sporadic out- 



