255 
in consequence of the operations of the silver-mining industry, and 
except some remnants in the less accessible ravines and side canyons 
only a few scattered trees, or, at best, groups of trees, are left. These 
trees, already more or less weakened by their isolated and exposed 
position are preferably infested by this beetle and succumb, one by one, 
to its attacks. 
In the mode of attack this Hylesinus sericeus does not differ from 
many other bark-boring Scolytidae. The female beetle bores a hole 
through the bark and constructs a longitudinal gallery just between the 
bark and the sapwood. During this operation she deposits the eggs at 
regular intervals along the two sides of the gallery. The young larvae 
commence to gnaw side galleries, which at first run horizontally, but 
gradually assume, or at least have a tendency to assume, a longitudinal 
direction. 
The acconrpanying figure (Fig. 25), which illustrates the work of three 
female beetles and their numerous progeny, renders all further descrip- 
tion unnecessary. It represents a small piece of the bark of Engel. 
mann's spruce (Pieea engelmanni), collected near Alta, at the head of 
Little Cottonwood canyon. The whole trunk of the tree was just as 
densely covered with these galleries as the small sample piece figured, 
and it is hardly necessary to remark that the tree had already succumbed. 
This scolytid appears to be readily attracted to trap trees, for I saw 
at the mouth of Big Cottonwood canyon a pile of freshly sawed spruce 
wood which was densely beset with the galleries, and I have no doubt 
that a few pieces of wood laid out at the proper season and properly 
attended to (£. e., decorticated before the larvre are full grown) would 
juotect the living trees for some distance around. 
Scolytid beetles in the imago state are very difficult to distinguish 
from each other, but in most instances the species can be readily reeog. 
nized from their mode of work; and this proves the importance of 
giving illustrations of the galleries. There is in the Eocky Mountain 
region no other pine-infesting scolytid* which constructs galleries 
similar to those of Hylesinus sericeus. 
The gallery figured above differs radically from those known to be 
made by other species of Hylesinus, and the following remarks are 
added as an explanation of this discrepancy: 
The species originally described by Mannerheim as Hylurgus seria us 
and subsequently referred by'LeConte to Hylesinus can not be retained 
in the latter genus. In Hylesinus the antennal club is distinctly com- 
pressed and the front coxae are widely distant ; the species live in decid- 
uous trees, and the gallery made by the female beetle is transverse. H. 
* The following species of seolytiche were observed in June, 1801, to live on Pioea 
engelmanni in the Wahsatch Mountains of Utah, at an altitude from 8,000 to 10,000 
feet: Hylastes macer , Hylesinus sericeus, Dendroctonus runpenni*. Scolytua unispinosus, 
Tomieus hudsonicus, Pityogenes earinulutus var., Cryphalu* intricattis. ('. ttriatulus 
P i ty oph thorns nitidulus. 
