DOUGLAS FIR PITCH MOTH. 5 
proves that it is fairly numerous, it is only by good fortune that one 
gets a chance to observe its behavior. During two seasons of 
judiciously chosen days and locations for observations the writer 
saw but six specimens in the forest. They were all females, and 
each of them was apparently engaged in oviposition. While the 
insect swiftly wings its way up and down the tree trunk, the eggs 
are deposited, either at the edge of a wound or a perfectly smooth 
spot, oftener the latter, and only a single egg is deposited at each 
place. 
In Montana, where the insect is not exceedingly numerous, the 
writer and Entomological Rangers Swartz, Wagner, and Fleming 
examined hundreds of trees, each of which displayed comparatively 
fresh, healed-over wounds, un- 
questionably of sesiid origin, but 
in no case was more than one 
larva of each of the triennial gen- 
erations found at the same time in 
the same tree. This suggests that 
if there is an abundance of suit- 
able trees for infestation a female, 
after depositing one egg only on a 
tree, leaves the latter, repeating 
the same operation until its sup- 
ply of eggs is exhausted. Conse- 
quently quite a number of trees are 
thus affected by a single female. 
From Ashland, Oreg., where Fic. 1.—Three generations of larve of 
the insect is much more abundant ah ae la een Ra Ce 
than in the Rocky Mountains, Mr. 
Edmonston reported as many as 6 larve, all of which proved to be 
of the same generation, from a single tree, and Mr. B. T. Harvey 
states that quite a number of trees in the coastal region are scarred 
from base to near the tops by the work of this moth. 
I have no doubt that this apparent discrepancy in ovipositing is 
due solely to the fact that in regions where the insect is nearly ten 
times as numerous as in the Rocky Mountains several females by 
chance deposit eggs upon the same tree; in fact, they are compelled 
to do so, unless they are willing to oviposit on trees that are unde- 
sirable on account of growth. 
By August 1 young larve from the June oviposition, upon close ex- 
amination of the infested trees, may be readily located by the boring 
dust, which resembles that of Dendroctonus pseudotsugae Hopk. 
This dust is produced by the larva eating its way through the outer 
bark into the cambium. At the end of the first active season a pitch 
tube covers the wound as well as the larva which made it. 
