INSECT ENEMIES OF WESTERN FORESTS 155 



H. longus Lee. is a dark reddish-brown species about % 6 inch long 

 which breeds in ponderosa pine in Colorado and New Mexico. H. 

 macer Lee. is a pitch-black species nearly 14 inch long, which 

 breeds in ponderosa, sugar, Jeffrey, and lodgepole pines and En- 

 gelmann spruce throughout the West. H. minutus Blkm. is a small 

 (% 2 inch long) dark reddish-brown to black species found breed- 

 ing in ponderosa pine and Douglas-fir in California, Oregon, and 

 Nevada. H. nigrinus (Mann.) is a dark-brown to pitchy-black 

 species slightly over 3 / 16 inch long, commonly found along the 

 Pacific slope and east to Idaho, breeding in Douglas-fir, true fir, 

 spruce, and western hemlock, and in shore, Monterey, and western 

 white pines. II. ruber Sw. is a bright, shiny, reddish-brown species 

 nearly 14 mcn l° n &> which is commonly taken in flight and is re- 

 ported from Douglas-fir in the Pacific Coast States, Idaho, and 

 Montana. 



Pseudohylesinus sericeus (Mann.) a small, stout beetle % inch 

 long, attacks weakened or dying shore pine and Monterey pine 

 along the coast of California and north to Alaska. Its egg tunnels 

 are short and longitudinal. 



FIR BARK BEETLES 



The true firs and Douglas-fir, as well as pines, have their full 

 share of bark-beetle enemies (13, 30). In general the destructive 

 species are different from those attacking pines, though many of 

 the secondary species may be the same. Douglas-fir growing under 

 favorable conditions in the commercial stands of western Oregon 

 and Washington seems to be resistant to bark-beetle attack, al- 

 though sporadic group killing in thrifty stands sometimes occurs, 

 especially after beetles have developed in fire-killed timber (96). 

 At times this tree suffers from bark beetles, even in this region of 

 favorable growth. In the eastern portion of the Douglas-fir range, 

 where growth conditions are less favorable and the timber is of 

 inferior quality, bark-beetle outbreaks of disastrous proportions 

 are not an uncommon occurrence. The Douglas-fir beetle causes 

 most of the damage. Small Douglas-firs are frequently killed 

 by the fir engraver beetles, particularly in situations where large 

 numbers of these small beetles have developed in windfalls or 

 slash. The engravers usually responsible for this type of damage 

 are Scolytus unispinosus or Pseudohylesinus nebulosus. 



The true firs are very susceptible to bark-beetle damage, and 

 in certain years outbreaks sweep through fir stands and kill a high 

 percentage of the trees. In such years it is not uncommon to see 

 entire hillsides turn red with the discolored foliage of dying trees. 

 Since true firs in the West have not been of great commercial value 

 until recently, no estimates have been made as to the extent of 

 such damage. 



In addition to aggressive tree-killing fir bark beetles, there are 

 also a large number of secondary species that breed in dying or 

 dead trees, slash, and broken tops. These, under exceptionally 

 favorable circumstances, may become destructive to living trees. 



The Douglas-fir beetle (Dendroctonus pseudotsugae (Hopk.) is 

 the most important bark-beetle enemy of Douglas-fir throughout 



