DOUGLAS FIR PITCH MOTH. 



11 



laths, cr firewood. Therefore to illustrate them adequately it would 

 be necessary to split tree trunks, often for the length of several logs, 

 to show a side view of an entire seam, and even if this were accom- 

 plished successfully the result would be merely something like a 

 board which had been split and had been loosely stuck together 

 again. With the exception of figure 2, showing the evolution of 



Fi<j. 5. — Wound caused by the Douglas fir pitch moth. Photographed 

 soon after emergence of moth. Natural size. (Original.) 



the pitch scam, the photographs used to illustrate the injury to 

 Douglas fir by pitch-moth infestation are from material from which 

 the insert emerged so recently that the cause of the wounds is 

 obvious. Such injury within the tissues of a coniferous tree is never 

 eliminated in the course of years, but rather becomes accentuated 

 when the split of the tissues is later extended for the length of many 

 feet by mechanical strain. 



