22 



SOME INSECTS INJURIOUS TO FORESTS. 



blame for the trouble. There were many trees which had been dead 

 for from 3 to 10 years, and in the bark of those dying within the past 

 4 years traces of the characteristic galleries of D. hrevicomis were 

 found. No large bodies of timber had died, but the dead and dying 

 trees were scattered all through the forest. A few examples of adults 

 were found mining in living bark of a dying tree, where they had 

 evidently passed the winter, since none of the broods had sufficiently 



matured to emerge. April 26, eight 

 large trees — five western yellow pine 

 and three sugar pine — which had evi- 

 dently died in 1897, were observed in 

 the Slate Creek Valley. The western 

 yellow pine exhibited abimdant work 

 of Dendroctonus irevicomis, and the 

 sugar pine the work of both this and 

 a larger species of the same genus 

 (D. monticolse). 



Buckeye, Wash, {near Spokane), 

 May 22. — A small western yellow 

 pine tree, evidently killed by the m- 

 sects, was found. None of the brood 

 had emerged, having died in the bark, 

 possibly from the effects of unfavor- 

 able climatic conditions. In another 

 tree killed by this species at this place, young living adults were 

 found. " 



Cedar Mountain, Idaho {near Moscow) , June 4. — The bark of western 

 yellow pine trees defoliated by pine butterfly larvae was found to- be 

 infested by larvte and pupae of D. Irevicomis. Dead parent adults, 

 also, were found in the primary galleries. 



Mariposa County, Cal., June 9, IPO.^.— Fragments of dead adults 

 were found in primary galleries in bark of a large western yellow pine 

 tree, evidently killed by this species. 



Yosemite Valley, California, June IS, 190^. — Western yellow pine 

 trees cut between September 20 and 24, 1903, were found to be 

 thickly infested with larvae of this species from eggs evidently de- 

 posited in September or October, 



OBSERVATIONS BY H. E. BTTBKE, 1904. 



From October 20 to 26, 1904, Mr. Burke found the work of this 

 species on western yellow pine quite abundant in the region of Smiths 

 Ferry, Idaho. Under date of October 26 he records observations 

 regarding this barkbeetle in a western yellow pine tree 3 feet in diam- 

 eter felled some time during that summer; the foliage and bark were 

 living, but red borings on the bark showed where insects had entered. 

 Adults of the Dendroctonus were p>'bwbihi: -m .■«;„.,, ;„,v,, . -, 



Fig. 10. — The western pine-destroying baric- 

 beetle ( Dendroctonus hrevicomis) : a, pupa, 

 ventral view; &, same, dorsal view. Ver- 

 tical line in center represents natural 

 length (original). 



