13 
ing and dying standing trees and the stumps of felled ones, and exca- 
vates a broad, crooked, longitudinal gallery. The eggs are deposited 
in masses along one side, and when they hatch the larve work together 
and excavate a broad chamber, instead of making individual larval bur- 
rows, as is the rule with most other species. One of the striking pecul- 
iarities of this insect is the habit of the adult and larva of living in 
the quantity of semiliquid pitch or turpentine which accumulates in 
the primary gallery and brood chamber. While this beetle is capable 
of attacking and developing its broods in the bark of a living, healthy 
tree, it seldom causes the death of trees unaided by other insects. It 
does, however, contribute to 
the death of trees attacked by 
the pine-destroying and other 
destructive beetles. It is a 
common insect in the Rocky 
Mountain region and west to 
the Cascades. A variety (Den- 
droctonus valens orientalis) is 
common in the Kast, attacking 
in the same manner all of the 
Eastern pines. 
The Western pine IHylur- 
gops (Lylurgops subcostulatus 
Mann.).—This is a common, 
dull brown to black bark beetle, 
ranging in length from 3.5mm. 
to 4.5 mm., which attacks and 
breeds in the bark on the roots 
and bases of dying trees and the 
stumps and logs of felled ones. 
It excavates a single longitudi- 
nal gallery, and the broods de- 
velop in confused or irregular 
larval mines in the inner bark, { 
* Fig. 5.—Work of the rock pine wood engraver (Pi- 
but rarely groove the surface tyogenes cariniceps Lec.). Primary galleries and 
of the wood. This is one of larval mines in inner bark and surface of wood. 
Reduced about one half (original). 
the commonest bark beetles 
from the Rocky Mountain region to the Pacifie coast, and will evi- 
dently be found wherever the rock pine or Western yellow pine grows. 
The pine-root bark-beetle (Hylastes porosus Lec.).—This is a black, 
elongate, slender bark beetle, varying in length from 4 mm. to 5 mm. 
It attacks the bark on the roots of the Western pine and excayates a 
single longitudinal gallery from which the brood burrows radiate, 
and the broods develop in the usual manner. It was found in the 
bark on the roots of young seedling pines which had recently died, 
