INSECT ENEMIES OF WESTERN FORESTS 151 
The ponderous borer (H'rgates spiculatus Lec.) is very destruc- 
tive to the wood of recently killed or felled coniferous trees, to 
fallen logs and stumps, and even to power and telephone poles. Re- 
cently it has been found to be a most important determining factor 
in the salvage of fire-killed Douglas fir. The heartwood of this tree 
is very resistant to deterioration until penetrated by the large mines 
of this wood-boring species. The adults are the largest of our 
western beetles, measuring from 11% to 214 inches in length (fig. 74). 
Figure 74.—Larvae and adult of the ponderous borer (HLrgates spiculatus). Natural size. 
The color is uniformly dark brown, with the head and thorax some- 
what darker than the elytra. The sides of the prothorax are armed 
with a few large or many small teeth or spines. They are often 
found flying around lights early in the summer. Eggs usually are 
Jaid in crevices of the bark of dead trees or stumps, and the larvae 
excavate large channels, packed with coarsely chewed wood fiber, 
in the sapwood and then into the heartwood. When full grown the 
large, thick-bodied larvae are often 214 inches in length, creamy 
white, with reddish heads bearing plates armed with four spines just 
above the mandibles. The species is found throughout the Western 
States, commonly attacking Douglas fir and pines but also other 
conifers. 
The California prionus (Prionus californicus Mots.) is another 
large species very similar to the foregoing. The larvae feed in the 
wood of oak, alder, poplar, and other hardwoods, sometimes boring 
into the roots of living trees. The adults usually have three promi- 
nent spines on the lateral margins of the prothorax. The larvae are 
very similar to those of Lrgates. 
