1:22 MISC. PUBLICATION 273, U. S. DEPT. OF AGRICULTURE 
The usual method of direct control is to fell the tree and cut the 
infested bole into logs, which are then decked and burned. As a 
large percentage of these insects overwinter as adults and emerge 
early in spring, fall control is the most effective. 
THE FIR-ENGRAVER BEETLES 
There are a number of small species of bark beetles, belonging to 
Scolytus, Pseudohylesinus, and other related genera, which commonly 
work under the bark and score the sapwood of dying, broken, or felled 
firs, but which at times may become so abundant and aggressive as to 
attack and killsmalltrees. This 
entire group may be referred to 
as “fir engraver beetles.” 
Members of the genus Scoly- 
tus, are small, shiny, dark, or 
nearly black bark beetles, which 
are easily recognized by the con- 
cave appearance of the posterior 
ventral surface of the abdomen. 
The adults feed for some time 
by making feeding pits in the 
twigs and later attack in pairs 
and construct short egg gal- 
leries, usually from a central en- 
trance chamber. The larvae 
work out at right angles from 
the egg gallery and bore through 
the phloem and inner bark, usu- 
ally deeply scoring the sapwood. 
Some members of the genus are 
exceedingly destructive to bal- 
sam firs. Others work in Doug- 
las fir, hemlock, spruce, or even 
in broadleaved trees. 
The Douglas fir engraver 
(Scolytus unispinosus Lec.) is 
re ee ee COOL ome UU ele Lay 
graver (Scolytus wnispinosus). weakened, injured, dying, OL re- 
cently killed Douglas fir in the 
Pacific Coast and Rocky Mountain States and southwestern Canada. 
Sometimes it 1s a primary enemy of young Douglas firs. The 
adults are small, black, cylindrical, shining bark beetles about one- 
eighth inch in length, with a long spine projecting from the middle 
of the nearly perpendicular face of the ventral declivity. The 
typical ege gallery follows the grain of the wood and may range 
in length from 114 to 3 inches. A short entrance tunnel leads into 
the main gallery, at an angle of 45°, and a small nuptial chamber 
is constructed at the juncture (fig. 60). The larvae work out at 
more or less of a right angle from the ege gallery, and then work 
up or down the tree so that the mines will not cross one another. The 
winter is spent in the egg and young larval stages. Emergence of 
adults takes place late in April, in May, June, and July. There 
appear to be two generations annually. 
