802 REPORT UNITED STATES GEOLOGICAL SURVEY. 



INSECTS INJURING SHADE AND FOREST TREES. 



Soimportiint to the Western Territories is the preservation and culti- 

 vation of forest, as well as shade and ornamental, trees, that a slight 

 sketch of what is known of the insects found in Colorado to be injurious 

 to them will be of some importance until more definite information is 

 obtained. On Plate LXX, I have given outline figures of a number of 

 insects either found living in forest-trees in Colorado, or, from the habits 

 of their allies in the Eastern States, supposed to be injurious. 



INJURING CONIFEROUS TREES. 



The Spruce-Timber Beetle, JDryocoetes affaber, Manuh. (Plate LXX, 



Figs. 1-3.) 



This beetle occurred (July 7) in abundance in all stages in a growth 

 of Abies mensiesii,* the common spruce of the Rocky Mountains, at 

 Kelso's Cabin, 11,200 feet elevation, on the road to Gray's Peak. It 

 bores into the back and near the sap-wood in all directions, its burrows 

 resembling those of Tornicus pini, with which it is associated, being 

 irregular, but much smaller. 



The larva (Plate LXX, Fig. 1) is of the usual form of those of the family, 

 being cylindrical and of the same thickness throughout, with the end 

 of the body full and suddenly rounded ; segments convex, especially 

 the thoracic ones, and slightly hairy. Head two-thirds as wide as the 

 body, rounded, honey-yellow. Length, 0.15 inch. 



The pupa is much like that of T. imii, with two anal soft, sharp 

 tubercles. As my specimens are farther advanced than those of T. pini, 

 the wings being free from the body, and the abdomen longer, it is im- 

 possible for me to draw up a good description. In one example, the 

 pupa had retained the larval head, but it was split behind so as not to 

 interfere probably with the development of the adult beetle. 



The beetle (Plate LXX, Fig. 3) differs from T. pini in its much smaller 

 and slightly slenderer body. The head and ijrothorax are two-thirds 

 as long as the rest of the body. The abdomen is not scooped out at 

 the end as in T. pini, but truncated, moderately rounded, and the end 

 of the abdomen reaches to the end of the wing-covers, which are square 

 at the end instead of excavated as in T. pini. Color reddish-brown, 

 much as in T. pini. The body is covered with fine, stiff, straight hairs. 

 Length, 0.14 inch. 



The Pine-Timber Beetle, Tornicus pini Say. Pupa and beetle. 

 (Plate LXX, Figs. 4, 5.) 



This timber-beetle was common, boring irregularly into the inner 

 bark of Abies menziesii. The burrows are like those made by the same 

 insect in the white pines from Maine to North Carolina. On the Atlan- 

 tic coast the more regular burrows radiate from a common center. 

 Those observed on Gray's Peak were 0.08 inch in diameter. 



In the pupa the body ends in two long, pointed, horn-like appendages 

 arising from each side beneath. The ends of the hind tarsi extend to 

 the terminal third of the wings. The antennre are clavate, not extend- 



*Tbis tree was kiudly identified for lue by Mr. Sereno Watson, from specimens of 

 the leaves and cones sent him for identification. 



