158 EXPERIMENT STATION RECORD. 



In order effectually to destroy the insect it is only necessary to remove the 

 infested bark from the trunks and burn it. 



The Arizona pine beetle {D. ai-izonicus) attacks western yellow pine in cen- 

 tral Arizona. The smaller Mexican jiine beetle (D. mcxicanus) and the larger 

 Mexican pine beetle (D. paralhUjcoUis) attack pine trees in Mexico. The 

 Colorado pine l)eetle (D. appro.viinatiis) attacks western yellow pine from cen- 

 tral Colorado and Utah to soutliern Arizona and New Mexico. The mountain 

 pine beetle {D. monticolw) attacks silver or western white pine, western yellow 

 pine, and lodgepole pine, in Montana, western Wyoming, Idaho, Oregon, and 

 Washington, and also sugar pine, western yellow pine, and lodgepole pine in 

 the mountains of Washington, Oregon, and California. The simple removal of 

 the bar(s without burning is sufficient to kill the broods of this species, 'llu; 

 infested trees should be located and marked in September and the infested bark 

 removed from the main trunks during the period from October to July. 



The Black Hills beetle (D. pomlerosw) attacks yellow pine, lodgepole pine, 

 limber pine, Mexican white pine, white spruce, and Engolmann spruce from the 

 Black Hills, South Dakota, to southern Arizona and westward into Utah, and 

 is very destructive. The bark should be removed from the main trunk of the 

 trees between October 1 and June 1. It appears to have been brought under 

 complete control within the radius of some hundreds of square miles in the 

 vicinity of Colorado Springs, Colo., through the felling and barking of trees 

 within the period necessary to destroy the bi'oods. At another locality in 

 Colorado where more than 250,000 ft. of timber was infested it was brought 

 under control through the cutting and barking of the timber or the destruction 

 of the slabs by burning, as recommended. 



The Jeffrey pine beetle [D. jeffreyi) attacks Jeffrey pine and yellow pine 

 in the Yosemite National Park and San Bernardino County, California. The 

 methods of -control are the same as for the two preceding species. The eastern 

 larch beetle (D, simplex) attacks eastern larch, from New Brunswick west- 

 ward to northern Michigan, and probably to the western and northern limit 

 of this tree, and south in the higher Alleghenies to northeastern West Virginia 

 and western Maryland. The infested trees should either be barked, burned, or 

 placed in water, and the stumps barked, during the period between September 

 and the following May. Trap trees felled during May and June should serve 

 to attract the beetles away from living trees and thus facilitate their destruc- 

 tion by removing the bark during the following fall and winter. 



The Douglas fir beetle {D. pseudotsugw) attacks Douglas fir, bigcone spruce, 

 and western larch, wherever these trees grow from British Columbia south- 

 ward into New Mexico, Arizona, and California. In order effectually to check 

 its ravages at least 75 per cent of the trees affected should have the infested 

 bark removed from the main trunks or the logs converted into lumber and 

 the slabs burned during the period beginning with the first of November and 

 ending the first of the following March. The eastern spruce beetle (Z>. jHcea- 

 perda) attacks the red, black, and white spruce from New Brunswick, Canada, 

 southward in the mountains of New York and Pennsylvania and westward to 

 Michigan. The removal of the infested bark from the trunks of the trees with- 

 out burning is all that is necessary to kill the immature stages of the insect at 

 any time. If the work be done during the period beginning with the middle 

 of October and ending with the middle of ]\Iay, say at or below an elevation of 

 about 1,800 ft. at latitude 45°, the parent adults and developed broods of adults, 

 together with the immature broods, will be killed. It is stated that the injury 

 to mature spruce in northwestern Maine appears to have been checked through 

 the concentration of logging operations in infested sections, as recommended 

 by the author. 



