20 MISC. PUBLICATION 7 4, U. S. DEPT. OF AGRICULTURE 



has periodically destroyed the timber over considerable areas. Sev- 

 eral recent outbreaks have occurred in the Sacramento Mountains. 

 Douglas fir is the favored host but spruce foliage is eaten as well. 

 Dendroctonus engelmanni frequently follows and destroys not only 

 weakened trees but vigorous stands outside the area of defoliation. 



THE LODGEPOLE NEEDLE TIER 



Argyrotaenia pinatubana Kearf. 



The lodgepole needle tier, supposed to be the same as the defoliator 

 of eastern white pine, became very abundant in 1920 to 1925 on the 

 headwaters of the Madison River in Yellowstone National Park 

 and the Madison National Forest. In conjunction with a sawfly 

 (Neodiprion sp.) these insects killed most of the lodgepole pine over 

 an area of 75 square miles. 



THE BROWN-TAIL MOTH 



Uygmia phaeorrhoea, Donovan 



The brown-tail moth is an insect which has been introduced and 

 become established in the New England States. It is locally and 

 periodically abundant, defoliating apple, pear, plum, oak, willow, 

 elm, maple, and other common trees and shrubs. It does not attack 

 conifers. The hairs from the caterpillars are a source of annoyance, 

 causing a rash and irritation of the skin (i#). 



THE DOUGLAS FIR TUSSOCK MOTH 



Hemerocampa pseudotsugata McD. 



This defoliator has come into prominence as an insect of economic 

 importance within the last ten years in the northern Rocky Mountain 

 regions, Washington, and British Columbia. Locally through this 

 region it has killed a great deal of Douglas fir, but the outbreaks 

 usually disappear in about three years. The female is wingless. 

 The caterpillars shed poisonous hairs which cause a rash on sus- 

 ceptible skins. 



OAK AND MAPLE DEFOLIATORS 



Eeterocampa spp. 



Caterpillars belonging to the genus Heterocampa occasionally be- 

 come exceedingly abundant in hardwood forests and severely de- 

 foliate trees over large areas. In 1918 and 1919 maple and birch 

 were severely defoliated in New Hampshire by Heterocampa bi- 

 lineata Pack, and H. biundata Walk., and elm in Essex County, 

 N. Y., by H. bilineata in 1918. H. guttivitta Walk, defoliated 

 maples, birch, and beech in New York, Vermont, and New Hamp- 

 shire in 1910 and 1919. E manteo Dbdy. defoliated forest trees, 

 oak, beech, maple, and hickory, in 1922 over an extensive area in- 

 volving Virginia and North Carolina. Many oaks were completely 

 stripped. In most of these defoliations caterpillars of more than one 

 genus were reported present although species of Heterocampa played 

 the dominant role (15, 25). 



