8 BULLETIN 295, U. S. DEPAETMENT OF AGRICULTUKE. 
stand of second growth. Yellow pine, lodgepole pine, and Douglas 
fir are the tree species thus far noted to be subject to infestation by 
this insect in the West. Out of a hundred trees so infested about 80 
per cent are yellow pine, 15 per cent lodgepole pine, and 5 per cent 
Douglas fir. Trees with a thick layer of fresh bark and cambium, as 
well as the more vigorous growers, are preferred for attack. All 
sizes, from but a few inches to several feet in diameter, are subject to 
infestation ; but it is the mature trees which furnish the most favora- 
ble means of existence for this moth, while in the smaller ones, up 
to about a foot in diameter, it does the greater damage. (PL V.) 
CHARACTER OF INJURY AND WORK OF LARV^. 
The moth, as a rule, attacks mature trees from between 10 to 30 
feet from the top down, and second growth from about breast high 
up to from 35 to 40 feet. Infestation nearer the top or base occurs 
only to a very limited extent. 
As stated under " Seasonal history" (p. 4), fresh infestation is 
only indicated by the castings on the surface area of the attacked 
trees. If this area is very heavily infested, as in the case cited above, 
where the writer found 27 nearly mature larvae in a space less than 
5 feet hi length by about 1 foot in width, there is at no time any other 
indication observable. The bark dries up without exuding pitch, as 
if scorched by extreme heat, and several years after the insect has 
vacated the bark drops off and the injury becomes manifest to the 
average passer-by. Usually, however, in such cases some larvse 
leave the point originally infested and bury themselves higher up 
near a branch of the same tree. The pitch tube at the entrance of 
this tunnel invites close examination of the entire tree, whereupon the 
less conspicuous, vet heavy infestation is almost sure to be detected. 
(Pis. VI and VII.) 
During the spring following infestation drops of pitch usually 
begin to ooze out of the tunnels in the bark and cover the surface of 
the average wound with a uniform, thin layer, somewhat similar in 
appearance to a liberal application of paint with a brush. The inner 
bark assumes a spongy appearance and gains in thickness, which 
tightens and even breaks the outer bark, together with the dried pitch 
covering it. The entire infested space finally presents a strikingly 
rough aspect which resembles the injury of no insect except Pissodes 
schwarzij which produces a similar effect at the base of trees. 
By repeated infestation at the border of the wound, in the course 
of years the tree is gradually girdled and the part above the collar dies 
and finally rots off at its base, provided the moth abandons the tree 
at this stage. But frequently infestation continues downward, on 
young trees usually until the lower branches, which by that time 
