INSECT ENEMIES OF WESTERN FORESTS 127 



Key to the Diagnosis of Insect Injury to the Inner Bark (Cont.) 



(1) Attacking 1 pine. Pine beetles. 



(aa) Egg galleries very winding, transverse, sub-trans- 

 verse, or longitudinal; crossing and recrossing to 

 form network of irregular channels; eggs isolated, 

 never in groups or masses; pupal cells in outer 

 bark 



(aal) Larval mines concealed in inner bark, ex- 

 cept for a short distance near the egg 

 galleries, which are winding and mostly 

 transverse or subtransverse. 

 Pacific coast and Northwest 



Western pine beetle, (D. brevicomis) , p. 132 

 Rocky Mountains and Southwest 

 Southewestern pine beetle (D. barberi) , p. 133 

 Arizona pine beetle (D. arizonicus) , p. 135 

 (aa2) Larval mines mostly concealed in outer 

 bark; egg galleries mainly longitudinal. 

 Colorado pine beetle (D. approximatus) , p. 135 

 (aa3) Larval mines exposed in inner bark; egg 

 galleries mainly longitudinal. 

 Roundheaded pine beetle (D. convexifrons) , p. 134 

 (bb) Egg galleries nearly straight to slightly sinuous, 

 longitudinal (following the grain), and long 

 (more than 10 inches), with L-shaped curve near 

 entrance; larval mines short and broad and 

 usually exposed in inner bark; eggs deposited 

 singly or in small groups along egg galleries. 

 Pacific coast, Northwest, and northern Rocky 



Mtns. . .Mountain pine beetle (D. monticolae) , p. 135 

 Rocky Mountains and Southwest 



Black Hills beetle (D. ponderosae) , p. 139 

 California — Jeffrey pine 



Jeffrey pine beetle (D. jeffreyi), p. 140 

 (cc) Egg galleries broad, irregular in width; eggs 

 deposited in masses; larval mines contiguous, 

 forming a broad larval chamber under bark at 

 base of trunks or in stumps ; large masses of pitch 

 at entrance holes. 



North America — in all pines 



Red turpentine beetle (D. valens) , p. 142 

 Northern Rocky Mountains — in lodgepole pine 



Lodgepole pine beetle (D. murrayanae) , p. 141 



(2) Attacking other conifers; egg galleries straight to 

 slightly winding, longtudinal, and usually short; eggs 

 placed in distinct alternate groups; larval mines long. 

 (aa) Larval mines separate throughout entire length; 



egg gallery averaging 8 to 16 inches long. Found 

 in Douglas-fir, western larch, and sometimes wes- 

 tern hemlock. Douglas-fir beetle (D. pseudotsugae) , p. 155 

 (66) Larval mines near egg gallery merging; in spruces. 

 Rocky Mountains and west 



Engelmann spruce beetle (D. eng elmanni) , p. 163 

 Alaska and Canada 



Alaska spruce beetle (D. borealis) , p. 164 

 North Pacific coast 



Sitka spruce beetle (D. obesns) , p. 164 

 6. Egg galleries under bark not packed with boring dust; indi- 

 vidual galleries consisting of one or two short (less than 6 

 inches) tunnels with entrance and nuptial chamber central 

 or at one end. 



