146 MISC. PUBLICATION 273, U. S. DEPT. OF AGRICULTURE 
Species of Gnathotrichus Hosts and distribution 
Gu retusus Leese e 2 a) Sea a Pines, hemlock, Douglas fir, and balsam firs. 
Western States and Canada. 
G:. sulcatus Veet see ee Spruce, hemlock, Douglas fir, and balsam firs, 
and sometimes also pines, redwood, cedar, 
and other conifers. Western States. 
Ge aciculatus 7 Bikim 2) eee ae Ponderosa pine, Mexican white pine, Douglas 
fir, and white fir. Rocky Mountain region. 
Gdenticuiatis Bikm=_ 222 oes k: Pines and white fir. New Mexico, Arizona, 
and Texas. 
Gonainiibikmes. 220s See ie re ornien Alder. Western Oregon and Washington. 
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FiGurE 72.—Tunnels of the oak timber beetle (Pterocyclon scutellare) and adults: Male 
above, female below, x 8 
The ambrosia beetles of the genus Trypodendron are small, stubby, 
dark-colored 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 Hosts and distribution 
TS TOtuintalim, Kirby a aes ae Nearly all conifers. North America. 
TP UT OTSUS IAT DY 2h eee me Lodgepole pine. Idaho, Montana, Oregon, 
and Washington. 
TD COG motse Mian = esses Pine, spruce, alder, birch, and cedar. Pacific 
Northwest, 
