INSECT ENEMIES OF WESTERN FORESTS lei 
insect enemy of this tree. It will also attack other species of spruce 
within its range, which covers Oregon, Washington, Idaho, Montana, 
Wyoming, the Black Hills of South Dakota, Utah, Colorado, Ari- 
zona, and new Mexico. Lar ge, overmature trees are preferred 
for attack, as are also trees weakened by mechanical injuries, logs, 
and windfalls. With large standing trees the base is seldom at- 
tacked, and examinations “must be made at a height of 6 feet or 
more from the ground if the insects responsible for the injury are 
to be found. 
The adult beetles are about one-fourth inch in length, reddish 
brown, with the body sparsely clothed with long hairs. They exca- 
vate a short, nearly straight, longitudinal egg gallery in the inner 
bark, slightly scoring the sapwood. The gallery is much wider 
than the beetles and is packed with boring dust, through which the 
adults keep a passageway open. LEggs are laid side by side in elon- 
gate cavities alternating from side to side of the egg gallery. The 
larvae at first bore out en masse, transversely from “the ege gallery, 
but later make separate mines. The pupal cells are usually con- 
structed in the inner bark, being exposed when the bark is removed, 
but are sometimes deeper in the bark, and quite concealed in thick- 
bark trees. 
There is only one complete generation annually, but it shows con- 
siderable overlapping of broods. ‘The winter is passed in all stages 
of development, except the pupal stage, with new adults predomi- 
nating, in trees attacked the preceding summer. The overwintering 
adults emerge rather early in the season, but the emergence from the 
overwintering larvae 1s spread over a rather long period, owing to 
variations in individual development. The time of emergence and 
attack will vary materially, according to differences in elevation 
and exposure, but the period of heaviest attack is in June and July. 
Since the developing larvae and pupae of this species are exposed 
when the infested bark is removed, such removal through peeling of 
infested trees will result in their destruction if the broods are in the 
larval or early pupal stage. The burning or severe scorching of 
infested logs is also an effective method of destroying the broods, 
especially when the beetles are in the adult stage. Owing to dense 
forest cover in most forests of Engelmann spruce the use Pof fire in 
beetle control will often be impractical because of the danger 
involved. As with the Douglas fir beetle, fall control is to be pre- 
ferred to spring control. 
The Alaska spruce beetle (Dendroctonus borealis Hopk.) attacks 
white and Engelmann spruce in Alaska and northwestern Canada. 
In appearance and habits it is very similar to the Engelmann spruce 
beetle, to which it is closely related. 
The Sitka spruce beetle (Dendroctonus obesus Mann.) is usually 
considered as a secondary enemy of the Sitka spruce, but it has the 
potentiality of becoming destructive. At times it has killed a con- 
siderable volume of Sitka spruce along the coast of Oregon, Wash- 
ington, and British Columbia. 
Many species of small engraver beetles which breed in the dying 
bark of felled or weakened trees sometimes become so plentiful as 
to become dangerous to small spruce trees and the tops of older 
