146 



MISC. PUBLICATION 273, U. S. DEPT. OF AGRICULTURE 



Species of Gnathotrichus Hosts and distribution 



G. retusns Lee Pines, hemlock, Douglas fir, and balsam firs. 



Western States and Canada. 

 G. sulcatus Lee Spruee, hemloek, Douglas fir, and balsam firs, 



and sometimes also pines, redwood, cedar, 



and other conifers. Western States. 

 G. aciculatus Blkm Ponderosa pine, Mexican white pine, Douglas 



fir, and white fir. Rocky Mountain region. 

 G. denticulatus Blkm Pines and white fir. New Mexico, Arizona, 



and Texas. 

 G. alni 'Bl^va Alder. Western Oregon and Washington. 



Figure 72. — Tunnels of tlie oalc timber beetle (Pterocyclon scutellare) and adults: Male 



above, female below, X 8. 



The ambrosia beetles of the genus Trypodendron are small, stubby, 

 dark-colorecl beetles, with a roundish prothorax and a smooth, more 

 or less shining body, often with lighter colored longitudinal stripes. 

 They attack the wood of many species of coniferous and broad- 

 leaved trees and are distributed throughout the greater part of the 

 United States and Canada. Their galleries (fig. 71) are of the 

 compound type with larval cradles arranged in series both above 

 and below the main tunnels, which branch in a horizontal plane 

 and cut across the grain of the wood. 



The species most frequently encountered in the Western States are 

 as follows: 



Species of Trypodendron 



T. Mvittatum Kirby 



T. rufltarsis Kirbv 



T. cavifrons Mann. 



Hosts and distribution 

 Nearly all conifers. North America. 

 Lodgepole pine. Idaho, Montana, Oregon, 



and Washington. 

 Pine, spruce, alder, birch, and cedar. Pacific 



Northwest. 



