37 



Those to be mentioned here are species of Gnathotrichus in pine, spruce, 

 Douglas fir, balsam, and hemlock of the Coast and Interior, and an undescribed 

 species of Platypus in spruce, Douglas fir, balsam and hemlock of the Coast 

 and Island regions. The Western Spruce Timber-beetle is abundant in conifers; 

 and other Ambrosia-beetles occur, but have not been found entering deep 

 enough into valuable timber to cause serious loss. 



The two most abundant Western Timber-beetles in conifers are Gnathotri- 

 chus retusus Lee. and Gnathotrichus sulcatus Lee. They are extremely abundant 

 in Douglas fir, western hemlock, balsam, pines, and probably occur in all conifers 

 throughout the province. They enter stumps, logs and injured and dying 

 trees. I have rarely found them entering in great numbers the trunks of hem- 

 locks with green foliage and apparently otherwise healthy; but this is certainly 

 not their normal habit. 



Fig. 20 A. Tunnels of Gnathotrichus sulcatus Lee. (G), and Platypus sp. (P) in Western Hem- 

 lock; la., larval cradles pointing up; lb., do. pointing down; e., eggs in ends of 

 Platypus tunnels. 



B. Sideview of portion of G. sulcatus tunnel: e.t., egg-tunnel; e.n., egg-niche; 1., 

 larva in cradle; p., pupa; a., young adult. 



The adults are elongate dark-brown beetles, one-eighth of an inch in length, 

 almost perfectly cylindric and smooth. The front of the pronotum is roughened 

 with scale-like asperities, and the elytra are sparsely hairy behind. 



The adult beetles excavate cylindric tunnels, about the diameter of a small 

 pencil lead, from four to about six inches into the wood. The entrance tunnel, 

 entering usually in the depth of a bark-fissure, passes directly through the 

 bark and into the wood for from one to two inches; there branching takes 

 place in a somewhat irregular fashion, though all parts of the set of tunnels 

 extend in the same horizontal plane. Usually one long side-tunnel is cut shortly 

 within the bark, parallel to the wood surface. The meal-like boring-dust and 

 excrement are extruded through the entrance hole. Along the inner tunnels 

 above and below, the females cut cup-like niches and deposit an elongate egg 

 in each. The larva which hatches from the egg lengthens the niche in which 

 it finds itself into a short tunnel, or larval-cradle, slightly more than its own 

 length when full-grown, and transforms therein to the pupal stage, with its head 

 towards the egg-tunnel. The pupa transforms to the adult in the cradle. The 

 chief food of the larvae, and an important food of the adults, is a peculiar fungus 



