THE GENUS DENDROCTONUS. 3 



experiments with trap trees. He also spent the season of 1906 in 

 the Black Hills to complete the investigations on the Black Hills 

 beetle and the season of 1907 in the national forests of southern New 

 Mexico and Arizona in general field work. 



Mr. Burke spent three seasons (1903, 1904, and 1905) in western 

 and northwestern Washington in general forest insect investigations, 

 and made observations on the Sitka spruce beetle (No. 17) and the 

 Douglas fir beetle (No. 13). He also made special trips to Idaho and 

 South Dakota in 1904 to determine certain facts relating to the west- 

 ern pine beetle (No. 1) in Idaho and the Black Hills beetle (No. 10) in 

 South Dakota. In 1906 he spent the greater part of the season in 

 the Yosemite National Park, under instructions to make special 

 studies of the mountain pine beetle (No. 9), the western pine beetle 

 (No. 1), and the red turpentine beetle (No. 23), and in 1907 he made 

 observations on the southwestern pine beetle (No. 2), the Black Hills 

 beetle (No. 10), and other species in the forests of Utah. 



Mr. Fiske gave special attention to the investigation of the south- 

 ern pine beetle (No. 4) and its work, experiments with trap trees, 

 etc., during his general investigations of forest insects in the South 

 Atlantic and Gulf States during the seasons of 1903, 1904, 1905, 

 and 1906, and studied the seasonal history and habits of the black 

 turpentine beetle (No. 22) and the red turpentine beetle (No. 23) — 

 the latter in the mountains of North Carolina. In the fall of 1906 

 he made observations on the eastern larch beetle (No. 12) and the 

 redwinged pine beetle (No. 18) in northwestern Michigan, and in the 

 spring of 1907 he made observations on species 4 and 22 in Texas 

 and on species 2, 3, 5, 8, 13, 15, and 23 in southern New Mexico. 



This field work by the writer and his assistants has resulted in 

 the accumulation of a mass of material in specimens and notes 

 which has served as a basis for the preparation of this part of the 

 bulletin. 



Considerable material has also been received from officials of the 

 Forest Service, together with information in regard to the location and 

 extent of depredations, and from owners of private forests and other 

 correspondents in different sections of the country who have notified 

 us of troubles affecting the timber and have responded to our requests 

 for specimens and detailed information in regard to the character and 

 extent of the depredations. 



DESTRUCTION CAUSED BY THE BEETLES. 



The results of our investigations have clearly shown that some of 

 the species of this genus of beetles are the most destructive enemies 

 of the coniferous forest trees of North America. As examples, we 

 have only to cite the well-known depredations by the eastern spruce 

 beetle (No. 14) in the northeastern United States and New Bruns- 



