20 BULLETIN 255, U. S. DEPARTMENT OF AGRICULTURE. 



means the practical dissociation of it from its neighbor, because the 

 dividing watershed line invariably provides unfavorable conditions for 

 moth existence on one slope. (See Habitat, p. 6.) Xo matter in which 

 direction a stream may flow, one slope of the watershed is always 

 subject to a greater degree of sunlight than is favorable to this insect. 

 Again, a sufficiently wide strip of trees other than Douglas fir on the 

 opposite side of a stream may safely be regarded as a buffer, as was 

 indicated in the results of investigations in Projects II, IV, and V. 

 Project V was an almost pure stand of Douglas fir which was con- 

 nected with the next nearest solid block of Douglas fir, about 1 mile 

 distant, by a few stragglers of this fir through the solid stand of sur- 

 rounding yellow pine. 



Small tracts, which can be given attention for a few days annu- 

 ally, may be kept comparatively free of infestation and, even if in- 

 fested, the removal of the larva during the first year of its life will 

 prevent the development of the wound to the serious stage. Of 

 course the infestation, even for only a year or less, will leave a pitch 

 spot in the tissue, just as is produced in case of unsuccessful Dendroc- 

 tonus beetle attack or the infestation by bark maggots, but the result 

 will not be nearly as serious as when the larva is left in the tissue to 

 complete its life cycle. From the investigation it also developed that 

 one experienced man could practically clean and keep clean an area 

 50 miles square or, roughly, 1,600,000 acres of this class of damage 

 within a few years. The long period of three years that is required 

 for the insect to develop from egg to adult is a decidedly strong fac- 

 tor in the case of its control. Considering the amount of annually 

 " loggable " Douglas fir from such an area under the mixed-stand 

 conditions that ordinarily obtain, and the percentage of depreciation 

 wrought by the insect, the employment of such caretakers would 

 appear to be a good investment, even if there were no other insect 

 problems requiring the attention of the men. 



If in the future lumbering interests are not to pay the same tax 

 to the pitch moth of our time as is now contributed, due to the 

 depreciation of timber a century and more ago, the present day is the 

 time to aid in the elimination of this pitch moth. 



As is apparent from the foregoing text relating to the larva and to 

 the seasonal history of the moth, two generations of larvae, excluding 

 the overlapping percentage at high altitudes and from late oviposi- 

 tion, may be found at any time of the year. For example, by July 1, 

 1915, the issue from the 1912 oviposition will have emerged and be- 

 tween that date and September 1, when the pitch tubes produced by 

 the issue of the 1915 oviposition are sufficiently developed to be 

 readily seen, only larvse from the 1913 and 1914 issue are to be 

 found. From September 1 until June 1, 1916, when the 1913 issue 



