13 



ing.and dying standing trees and the stumps of felled ones, and exca- 

 vates a broad, crooked, longitudinal gallery. The eggs are deposited 

 in masses along one side, and when they hatch the larvae work together 

 and excavate a broad chamber, instead of making individual larval bur- 

 rows, as is the rule with most other species. One of the striking pecul- 

 iarities of this insect is the habit of the adult and larva of living in 

 the quantit}^ of semiliquid pitch or turpentine which accumulates in 

 the primaiy gallery and brood chamber. While this beetle is capable 

 of attacking and developing its broods in the bark of a living, healthy 

 tree, it seldom causes the death of trees unaided by other insects. It 

 does, however, contribute to 

 the death of trees attacked by 

 the pine-destroying and other 

 destructive beetles. It is a 

 common insect in the Rocky 

 Mountain region and west to 

 the Cascades. A variety (Den- 

 droctonus valens orientalis) is 

 common in the East, attacking 

 in the same manner all of the 

 Eastern pines. 



The Western pine Tlylur- 

 gops (Hylurgops subcostulatus 

 Mann.). — This is a common, 

 dull brown to black bark beetle, 

 ranging in length from 3. 5 mm. 

 to 4.5 mm., which attacks and 

 breeds in the bark on the roots 

 and bases of dying trees and the 

 stumps and logs of felled ones. 

 It excavates a single longitudi- 

 nal gallery, and the broods de- 

 velop in confused or irregular 

 larval mines in the inner bark, 

 but rarely groove the surface 

 of the wood. This is one of 

 the commonest bark beetles 

 from the Rocky Mountain region to the Pacific coast, and will evi- 

 dently be found wherever the rock pine or Western yellow pine grows. 



The pine-root bark-oeetle {Hylastes porosus Lee.).— This is a black, 

 elongate, slender bark beetle, varying in length from 4 mm. to 5 mm. 

 It attacks the bark on the roots of the Western pine and excavates a 

 single longitudinal gallery from which the brood burrows radiate, 

 and the broods develop in the usual manner. It was found in the 

 bark on the roots of young seedling pines which had recently died, 



Fig. 5.— Work of the rock pine wood engraver (Pi- 

 tyogenes cariniceps Lee). Primary galleries and 

 larval mines in inner bark and surface of wood. 

 Reduced about one half (original). 



