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



Remembering that in the comparatively small zone about Rainy 

 Lake infested by the pitch moth there are tens of thousands of trees 

 with heavy pitch exudation at their base which, once ignited, will 

 burn, for several days, ram or shine, and that during the violent 

 thunder storms there many trees are struck by lightning and the 

 pitch set on fire, we will have the combination which explains the 

 frequency of fires in that area. 



Let us illustrate. Lightning strikes a tree infested by Vespamima 

 and sets it afire. During the storm the ground is soaked sufficiently 

 to prevent the fire from spreading. The pitch, however, owing to its 

 thickness and inflammability, continues to bum. On the following 

 day a clear sky allows the sun to dry the ground cover around the 

 burning pitch sufficiently so that a surface fire is started which will 

 be ended by the next shower. If the stand consists of medium or 

 small sized trees and the area has passed through fires before, every- 

 thing is killed, and the place, when it has been reforested, will stand 

 out clear in the checkerboard of forest and elemental battles even 

 after half a century or more, as is the actual case in this territory. 



As storms are evidently quite frequent there, the patches burned 

 are usually small, ranging from 50 to 200 acres. However, there are 

 also some burns which an accumulation of debris had undoubtedly so 

 augmented that whole sections were swept. All the traceable evi- 

 dence in the biggest burn in the area points to insect work as the 

 primary cause, just as in the smaller burns where the evidence is 

 more definite and is easier of location. 



With a knowledge of these facts, one can not but conclude that the 

 peculiar results of the work of Vespamima sequoia are the chief and 

 primary contributing cause of the frequency, we might almost say 

 continuity, of fire damage to forest growth in tins area. To eliminate 

 or ameliorate this condition, it is manifestly necessary to eliminate 

 the insect or at least reduce it to such an extent that it loses its 

 menacing aspect. 



REMEDY. 



Since nature and its agencies are powerless in the control of this 

 insect, the scourge has to be combatted by man through direct action 

 if it is not to continue its injurious activity in the future as it has in 

 the past. There is only one way to reduce the insect, and that is to 

 destroy it while it is. in the larval stage. 



As is apparent from the portion of this bulletin relating to the life 

 history of the moth, larvse can be found in the infested trees at any 

 time of the year. 



However, in order to destroy the greatest number of them with the 

 same amount of effort, operations should be conducted during the 

 months of September to June, inclusive, when there is no snow on the 



