DOUGLAS FIR PITCH MOTH. 7 
LOCATION OF AFFECTED AREAS. 
The Douglas fir pitch moth has apparently a very marked habit 
concerning the preferred areas in given localities. An area in which 
it is depreciating the timber now may be readily located by simply 
watching the logs at the mill as they go through the saw and ascer- 
taining where those with pitch seams come from. It may seem a 
matter of speculation to undertake to determine localities where the 
insect is numerous at present by thus examining trees which have 
been infested a century or more in the past, but it has been ascer- 
tained to be an absolutely reliable method. The success of this test 
not only proves that the sesiid is the cause of the depreciation, but 
it shows us in addition how we may determine the exact localities 
where the merchantable timber is lable to serious damage by the 
insect, because wherever the injury exists in the young, growing 
timber, which will be “‘loggable” a hundred years from now, it is 
pr actically certain that the mature trees had been afflicted in the same 
manner in their youth. 
' RANGE OF THE INSECT. 
As already indicated, the range of this insect is over the northern 
Rocky Mountain and Pacific Coast regions and extends in all proba- 
_ bility through the entire native range of the Douglas fir. From mv 
own observations and numerous field notes and from larve collected 
in various parts between the northern boundary of the United 
States and latitude 41° 30’ N. and from the eastern boundary of the 
State of Montana to the western coast by other members of the 
Branch of Forest Insects and kindly put at the disposal of the writer, 
it is evident that the moth is most abundant in the western part of its 
range, a conclusion which in turn is verified by the losses estimated 
by millmen in the various sections of this area. 
HOST TREES AND CHARACTER GF INJURY. 
(Figs. 2-5.) 
Douglas fir (Pseudotsuga tavifolia) is evidently the special host 
of this moth. However, although unable successfully to attack 
previously uninjured larch (Larix occidentalis) it breeds also and 
thrives well in blazes and other wounds on that tree, particularly in 
the pitch flow caused by a fungus, identified by Dr. James R. Weir, 
of the Bureau of Plant Industry, as Trametes pint. A great number 
of fungus-infested larch in a stand of timber may make this tree a 
real menace to the Douglas fir in the same area. 
The healthier and quicker growing a Douglas fir may be, the more 
it appears to be subject to infestation by the moth. Trees are at- 
tacked when about 10 years old and after that until they are about 
