22 BULLETIN 255, U. S. DEPARFMENT OF AGRICULTURE. 
On account of the long life cycle of the Douglas fir pitch moth its 
elimination, in any country where forestry is sufficiently advanced to 
be a profitable business and where the forests are taken care of as 
they should be in order that they may be profitable, will follow. In 
the range of the Douglas fir there are millions of acres of forest land 
which are inaccessible and practically worthless at the present day, 
but they will remain so not much longer, and with advanced methods 
in forestry Sesia novaroensis is bound to disappear ultimately. The 
process of its eradication will necessarily be slow, but this is no reason 
why a systematic policy to attain this result should not now be 
adopted in areas which have been and are being logged and which, it 
is certain, will be logged again when the reproduction attains mer- 
chantable size. | 
While in this paper only the more serious result of pitch-moth 
infestation during the first 40 years’ growth of trees is considered, it 
does not mean that the insect does no damage in older and mature 
trees. As is seen under “ Host trees,” it infests these also under 
favorable conditions, but in such cases the infestation results only in 
the so-called **gum spots,” the pitch blisters being too near the 
surface of the trees to cause serious breaks and ultimate “ pitch 
seams by mechanical strain in the part of the tissues rendered in- 
flexible. In regard to the * gum. spots” in Douglas fir, which entail 
practically no loss to mills, but for which the builder and consumer 
foots the bill entirely, the pitch moth is responsible for not more 
than 10 per cent, Dendroctonus pseudotsugae for not less than 70 per 
cent, and all other causes for about 20 per cent of the damage. 
