20 SOME INSECTS INJURIOUS TO FORESTS. 



EAHLT HISTORY OF THE SPECIES. 



LeConte, in 1876, described the species under the name Dendroc- 

 ionus hrevicomis from a single specimen collected in middle California. 

 Dietz, 1890, considered D. hrevicomis the same as the southeastern 

 species, D. frontalis Zimm. Hopkins, 1899, concluded that it was 

 distinct from D. frontalis, and therefore that the old name should be 

 retained. 



It appears that previous to 1899 nothing had been recorded in 

 regard to the habits and life history of this insect, and that, therefore, 



the earliest records were made in 1899 

 by Hopkins, who found it associated 

 with dying sugar pine and western yel- 

 low pine at McCloud, Cal., on April 21, 

 1899, and the next day at Grants Pass, 

 Oregon, with several hundred pine trees 

 whichhad evidently died from its attack. 

 On May 20, also, at Buckeye (near Spo- 

 kane), Wash., many trees were found 



Fig. 9.— The western pine-destroying i-i j ■ t.jj'j 



barkbeetle (Dendroctonus bremcomU): WhlCh were dying, or had died, as eVl- 



Larva. Line below represents natural denced by the abundance of the insects 



and the extent of their work, and on June 

 6, at Cedar Mountain, Idaho, Doctor Hopkins found it in the bark of 

 pine trees which had been defoliated the previous year by the cater- 

 pillars of the pine butterfly (NeopJiasia menapia Feld.). He found 

 also that this beetle was quite intimately associated with the destruc- 

 tion of a large amount of timber only partly defoliated by the cater- 

 pillars. 



Under his discussion of the principal scolytid enemies of the forests 

 in the Northwest, Doctor Hopkins refers to this species as follows : " 



Dendroctonus brevicomis Lee. was found to be a most destructive enemy of the yellow pine 

 {Pinus ponderosa) in northern California, southern and eastern Oregon, northeastern 

 Washington, and western Idaho. A large amount of some of the finest timber in all of 

 these localities had died within the past seven or eight years, evidently as a direct result of 

 attacks by this bark beetle. It was also found to attack and prevent the recovery of trees 

 injured by defoliating insects and other causes. Its habits and the character of its galleries 

 appear to be identical with those of Dendroctonus frontalis, which is noted for its destruction 

 of vast quantities of pine and spruce timber in West Virginia and adjoining States between 

 1890 and 1893. It is killing the western yellow pine just as D. frontalis commenced to kill 

 the eastern yellow pine {Pinus echinata) before it spread to all the other pines and spruce. 

 Therefore, just as D. frontalis has proven to be the most destructive enemy of eastern 

 conifers, the western representative of this species will doubtless prove to be, under similarly 

 favorable conditions, equally as destructive to the western forests in which the conifers 

 predominate. 



Among the most important features observed regarding the habits of this beetle was the 

 fact that it is attracted to trees girdled by settlers and farmers in the process of clearing land, 

 and that in the bark of such trees it breeds and multiplies in sufficient numbers to enable it 



a Bui. 21, n. s., Div. Ent., U. S. Dept. Agric, 1899. 



