6 MISC. PUBLICATION 7 4, TJ. S. DEPT. OF AGRICULTURE 



breaks, in which large groups of young trees and occasionally mature 

 trees are killed, often follow drought, windfalls, and slashings. 

 Epidemics will not continue in healthy timber because the broods 

 fail to develop, and such outbreaks as occur are short-lived. In 

 the southern part of the United States the three most important 

 species of Ips are grandicollis Eichh., calligraphus Germ., and avul- 

 sus Eichh. In the Western States confusus Lee, emarginatus Lee, 

 integer Eichh., oregoni Eichh., and radiatae Hopk. are the most 

 destructive species. /. oregoni very commonly kills the tops of 

 mature western yellow pines, rendering the trees susceptible to the 

 attack of Dendroctonus beetles (1, Jfi, 58, 63, 66) . 



MONTEKEY CYPRESS BARK BEETLE 



Phloeosinus cristatus Lee. 



Several species of Phloeosinus, a genus of bark beetles, apparently 

 are capable of killing trees belonging to those genera allied to 

 Cupressus. This species seems to be particularly aggressive in 

 Monterey cypress planted in the vicinity of San Francisco. It is 

 usually associated, however, with scale insects and fungi, and its 

 specific role has not been accurately determined. 



THE HICKORY BARK BEETLE 



Scolytus quadrispinosus Say 



The hickory bark beetle is an important enemy of hickory in the 

 Eastern States. Every few years local outbreaks of the hickory 

 bark beetle destroy considerable timber in the natural range of the 

 tree from Massachusetts southward to Georgia and westward into 

 the Mississippi Valley. Recent studies indicate that these out- 

 breaks are correlated with droughts or conditions unfavorably af- 

 fecting the trees (%, 43). 



THE FIR BARK BEETLE 



Scolytus ventralis Lee. 



This species, widely distributed throughout the Western States, 

 attacks standing dead, dying, or living firs, frequently killing them 

 but more often destroying only the tops of the trees or patches of 

 bark on the trunk, which results in defects. In California, following 

 the drought of 1924, very extensive losses were reported (40, 46) • 



INSECTS BORING IN LIVING TREES 



THE SMALL METALLIC WOOD AND BARK BORERS 



Agrilus anxius Gory 

 Agrilus bilineatus Web. 



The bronze birch borer (Agrilus anxius Gory) is very destructive 

 to several species of birch (Betula) in the Northeast. Its control 

 is becoming an important problem in the management of hardwood 

 stands. The 2-lined chestnut borer (A. bilineatus Web.) is of sec- 

 ondary importance throughout the eastern part of the United States. 

 It occasions the death of oaks weakened by other causes, though in 

 Minnesota it is reported to be more of a primary pest (8, 14, 57, 59) . 



