INSECT ENEMIES OF WESTERN FORESTS H^ 



The smaller ^^estern pine engraver {Ips latidens Lee.) usually 

 confines its attacks to the tops and limbs of dying or weakened 

 pines and seldom causes any primary injury. Under favorable con- 

 ditions, however, it has demonstrated its ability to kill trees, par- 

 ticularly those weakened by mistletoe or drought, and in some 

 instances even healthy trees of small diameter. It is quite common 

 in the tops of lodgepole pines killed by Dendroctonus beetles, and 

 during severe epidemics of the mountain pine beetle it often de- 

 velops in such numbers as to attack and destroy many small trees 

 throughout the area. The adults are the smallest of the western 

 species and are about one-eighth inch in length. They are distin- 

 guished by having three small, spinelike teeth along the margin of 

 the elytral declivity, which is nearly vertical. Its typical work 

 consists of from two to five rather short, sometimes curved, ^gg 

 galleries radiating from the central nuptial chamber. It is distrib- 

 uted throughout most of the Western States, where it attacks pon- 

 derosa, sugar, digger, lodgepole, western white, and probably other 

 species of pine. /. guildi Blkm. is a closely related form which 

 attacks lodgepole and probably other pines in Colorado and the 

 central Rocky Mountain region. 



The sawtooth pine engraver {Ips integer Eichh.) is distributed 

 throughout the Western States, but is found most commonly in the 

 Rocky Mountain region. It generally breeds in weakened or felled 

 ponderosa pine, lodgepole pine, western white pine, and western 

 larch, but under favorable conditions it may become primary. The 

 stout, brownish-black adults are about one-fifth of an inch in length 

 and have four spinelike teeth along the margin on each side of the 

 concave elytral declivity. This species constructs three or four straight 

 longitudinal Qgg galleries that fork from the common entrance or 

 nuptial chamber. The Qgg niches are so thickly and evenly spaced 

 along the sides of the egg galleries as to give these a sawtoothed 

 appearance — a distinctive feature of this species' work. 



The California pine engraver {Ips plastographus Lee.) is a species, 

 closely related to /. integer^ Avhich prefers to attack the trunks and 

 branches of felled Monterey, Bishop, and lodgepole pine, but at 

 times also attacks weakened or dying standing trees. It is not often 

 primary in its attacks, but is usually associated with the Monterey 

 pine engraver and the red turpentine beetle in the killing of living 

 trees or trees injured by fire or other causes. It is found through 

 the range of its host trees in the coastal belt of middle California 

 and in the Sierras. The adults are about one-fifth of an inch in 

 length, with four pairs of spines on the posterior margin of the 

 wing covers. The work pattern is very similar to that of /. confusus^ 

 the typical form having three, egg galleries from 5 to 15 inches in 

 length, issuing from each entrance chamber. There are from three 

 to five generations annually, depending on the locality and season. 



The Oregon pine engraver {Ips oregoni Eichh.) is probably the 

 most common Ips beetle found throughout the Western States, where 

 it attacks ponderosa pine, lodgepole pine, sugar pine, Jeffrey pine, 

 digger pine, and probably other species (fig. 56). Large numbers 

 develop in such host material as windfalls, freshly cut logs, pieces 

 of slash over 2 inches in diameter, and in the tops and limbs of 

 trees killed by Dendroctonus beetles. When conditions are favor- 

 able and suitable host material is plentiful, they frequently develop 



