14 BULLETIN 255, U. S. DEPARTMENT OF AGRICULTURE. 
This has to be borne by future generations, just as the present is 
paying for the damage inflicted by the insect a century or more in the 
past. 
Actual tally of sesiid wounds, blazes, bullet wounds, bruises by 
blasting, etc., all of which cause blister effects in wood tissue, was 
Hic. 8.—An embryo pitch seam caused by the Douglas fir pitch moth 
only a few years after emergence of moth: A, Pitch blister which 
the larvie caused before emerging; B, a break in the tissues by 
wind strain on account of the defect; C, break filling with pitch; 
D,.inclosed pitch from pitch tube which caused imperfect heal- 
ing; H#, parts of pitch tube which covered the larve, still part of 
the surface covering. Reduced. (Original.) 
made in a stand of Douglas fir about 30 years old, where conditions 
were most favorable for the operation of all the latter causes. This 
tally demonstrated that in this area of about 30 acres the sesiid 
wounds averaged, up to 15 feet from the ground, a little over 96 per 
cent, while the wounds from all other causes combined represented 
less than 4 per cent. Wounds above 15 feet could safely be consid- 
