112 MISC. PUBLICATION 273, U. S. DEPT. OF AGHICULTUPvE 



SO mucli as does the lack of suitable host material. Given a quantity 

 of freshly cut slash or Avindfalls, a large beetle population is 

 almost certain to be produced but it will not long survive after 

 the supply of this material is exhausted. 



Since outbreal^ in standing, healthy trees are sporadic and of short 

 duration, the destruction of the broods in these trees, through the 

 application of control methods, seldom contributes a great deal 

 toward reducing the damage. Efforts should be directed toward 

 preventing outbreaks by eliminating all situations favorable to the 

 development of excessive progeny. Thus, slash should be piled and 

 burned before the I])s beetles emerge, or scattered in the open where 

 the sun will dry it out and make it unsuitable as a breeding medium. 

 If it should be necessary to destroy broods in standing trees, the most 

 economical and effective method is to fell the trees and burn or scorch 

 the infested bark. A large number of species of this genus are 

 recorded from western pines, all very similar in appearance and 

 habits, so only a few of the more common species need be mentioned 

 here. 



The western six-spined engraver (//?5 ponderosae Sw.) is a second- 

 ary enemy of ponderosa pine, which for the most part attacks trees 

 that have been felled or those dying from attacks of more ]3rimary 

 species of bark beetles. The adults are about one-fourth inch in 

 length, reddish brown to black, with six spines on each side of the 

 elytral declivity. The gallery pattern consists of from two to five 

 egg galleries extending up and down the tree from the central nuptial 

 chamber. Though the pattern is similar to that of /. oregoni^ the 

 galleries are distinctly wider. This beetle has been recorded from 

 Arizona, California, Montana, and South Dakota, and undoubtedly is 

 present in other Western States. 



The California five-spined engraver {Ips confusus Lee.) is destruc- 

 tive to tops of mature trees, small poles, and the saplings of various 

 pines in California and southern Oregon west of the Cascade and 

 Sierra Nevada ranges. It breeds readily in slash and felled logs, and 

 the broods from such material often cause extensive damage to the 

 young pine growth in the vicinity. It commonly attacks ponderosa 

 pine, sugar pine, western white pine, Coulter pine, Monterey pine, 

 and less frequently other pines within its range. 



The adults are reddish brown to pitch black, about one-eighth inch 

 long and with five spines on the margin of each side of the elytral 

 declivity. The ^gg galleries usually comprise from three to five 

 nearly straight tunnels radiating from a central entrance chamber. 

 The typical form has three galleries in the shape of an inverted Y. 

 These galleries are not packed with boring dust and are usually from 

 5 to 10 inches long. Attacks are started early in the spring and from 

 two to five generations of beetles may develop during the summer. 

 In the northern part of the range, at an elevation of about 3,000 feet, 

 there are usually two summer generations which develop in fallen 

 logs and a third, or overwintering generation, which develops in 

 standing trees. At lower altitudes and in the southern part of the 

 range there are from three to five summer generations. The beetles 

 overwinter mostly in the adult stage, under the bark of recently killed 

 trees and probably in crevices and under litter on the ground. 



