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



SECONDARY INJURY BY FIRE. 



About one-half of 1 per cent of the trees infested by Vespamima 

 sequoia is killed. In case of a slight surface nfeiti places where, out- 

 side of humus, no litter covers the ground, all the infested trees which 

 are not killed outright come through it with the bark on the sides 

 where the pitch exudation is located literally cooked, and for the 

 balance of their existence they display the "fire wounds" (fig. 5), of 

 which the pitch moth was the primary cause. They remain green 

 but add little to their size annually. Subsequent fires fell them 



Fig. 5.— Fire wounds on pine tree injured by the Sequoia pitch moth. (Original.) 



readily, and their burning injures and kills perfectly healthy trees, 

 which would otherwise have remained unscathed. 



There is abundant proof in the area under discussion that unat- 

 tacked trees, on ground not littered with fallen timber, pass through 

 surface fires with but slight injury. Thousands of such trees are 

 mingled with as many which display "fire wounds" and the tunnel of 

 Vespamima burned indelibly into the base of the latter, thus explain- 

 ing why it is that some trees are half burned while others, under the 

 same conditions and at the same place, have escaped with scarcely a 

 scar. 



