4 BULLETIN 111, U. S. DEPARTMENT OF AGRICULTURE. 



1 -year-old larvae were abundant. If this observation holds good, 

 the insect being biennial, we should be able to forecast the years 

 when it will be abundant and when scarce. Hence there should be 

 great nights during 1914, 1916, 1918, etc., unless the insect is con- 

 trolled, and small flights during 1915, 1917, 1919, etc. 



RELATION TO THE MOUNTAIN PINE BEETLE. 



The only insect which is of any consequence in its relation to the 

 pitch moth in the Clearwater country is Dendroctonus monticolae 

 Hopk. This beetle frequently attacks trees infested by the- larvae 

 of the moth. This attack is always fatal to the latter, because 

 Dendroctonus kills the tree almost immediately, and without the flow 

 of sap the larvae of the moth can not survive. On October 1 every 

 larva of the moth which was found in trees attacked by the beetle 

 after August 1 was dead. Some of the trees had the appearance of 

 having been infested by the beetle only two or three weeks; never- 

 theless, the moth larvae were dead, although they were in perfectly 

 fresh condition otherwise. 



Vespamima sequoia is apparently little subject to attack by either 

 parasitic or predaceous enemies. In fact, it is less troubled by insect 

 enemies or diseases than any other species known to the writer; and 

 as birds also never seem to pursue it, there is no present evidence 

 that natural agencies might check it in the course of time. 



HABITAT. 



The insect prefers sunny openings within the forest and slopes 

 where the soil is rather sandy and quick to dry. Ridges along 

 watercourses are also favorite places for it. It avoids the damp and 

 densely shaded bottom lands along streams. It prefers pine, open 

 stands of lodgepole pine, as, for example, within and alongside the 

 big old burn which extends from the wagon road toward and along 

 the Flathead Range, where there are few trees 3 or more inches in 

 diameter that have escaped attack and are not infested now. 



HOST TREES, AND CHARACTER OF INJURY. 



Lodgepole pine is numerically the principal species of tree in the 

 region and, with the rare exception of the yellow pine, is the species 

 subject to attack by the pitch moth, although the moth attacks 

 almost all kinds of conifers in other localities within its range. 



The trees infested by this insect (see fig. 2) are readily located by 

 the never-absent pitch exudation over the tunnel of the larva. This 

 may be readily seen at quite a distance, if the stand of trees is not 

 too young. Even on very small trees of but 1 or 2 inches in diameter 

 the pitch tube is of the size of a walnut the first season of the infesta- 

 tion and more than twice that the second year. 



The pitch exudation on the tree shown in figure 3 weighed over 

 10 pounds, and such trees are so numerous that many tons of pitch 



