DOUGLAS FIR PITCH MOTH. 17 



usually indicates the presence of the larva. Plural infestation un- 

 der one pitch tube has not as yet been observed. 



It is only upon very close examination of the tree that the infesta- 

 tion will be revealed, so perfect is the blending of color of the Doug- 

 las-fir pitch and the bark, notwithstanding the fact that the covering 

 pitch tubes are about 2 inches in diameter and protrude at least 1 

 inch from the surface of the bark. The protuberances so much re- 

 semble a knobby growth that considerable experience is necessary 

 to enable one to distinguish- them at sight. 



The attack is restricted to the main trunks of trees, the first, 

 second, third, and fourth logs being usually most affected, the injury 

 becoming notably absent above 60 feet from the ground. 



Trees are never killed outright, although very vigorous trees r if 

 attacked several seasons in succession, become so weakened that their 

 originally less robust neighbors easily outgrow them. 



RELATION TO OTHER DESTRUCTIVE INSECTS. 



In most localities where the Douglas fir pitch moth is present 

 Douglas fir and larch trees are to be found with dead bark on the 

 trunks in strips several inches wide and often more than 20 feet 

 long. This peculiar injury, except in the case of Tetropium in larch, 

 is usually attributable primarily to fires, bruises by falling trees, and 

 perhaps, to some extent, lightning. Examination of these strips 

 under the bark usually reveals sesiid larvae, or at least abundant 

 traces of their work. The galleries under the bark contain, in addi- 

 tion, the unmistakable evidence of beetle infestation. In all such 

 cases coming under the writer's observation these beetles of the 

 genera Melanophila or Tetropium were found to have infested the 

 trees primarily or after they had sustained the mechanical injuries 

 before mentioned, and to have been the agents which prepared favor- 

 able propagating places for the moth. Extended observations lead 

 the writer to believe that these and similar beetles do not follow the 

 moth, but that the moths occasionally adopt the galleries, etc., of the 

 beetle-. 



A few trees which had been outstripped by their companions, evi- 

 dently on account of previous moth infestation, were noted as subse- 

 quently killed by Scoli/fuH itninpinosux, but, considering that these 

 trees when killed l»y the beetles were already worthless as timber 

 producers, the interrelation of moth and beetle in this instance seems 

 of no economic consequence. 



Vespamvma sequoia 7 is another very injurious pitch moth which 

 infests Douglas fir in 'ild wounds and branches, and especially wounds 



Brunner, .!..-■ t, The Bequola pitch moth. r. s. Dept. Agr., Bui. Ill, n p., r> flg., July 

 1 1. 101 I. 



