INSECT ENEMIES OF WESTERN FORESTS 39 
Dioryctria abietella D. and S. is a gray moth about three-fourths 
of an inch in length. The reddish caterpillars feed in the twigs and 
cones of knobcone, lodgepole, western white, sugar, and ponderosa 
pines, and many of the balsam firs. There appear to be two annual 
generations. 
The Zimmerman pine moth (Pinipestis zimmermani Grote), a me- 
dium-sized moth, light to reddish gray, closely related to the above, 
is reported by Brunner (9) as being destructive to all coniferous trees, 
especially ponderosa pine, throughout the Pacific Northwest. He 
credits the “spike top” of mature trees and the spike top, stunting, 
and destruction of smaller trees, to the work of this insect. However, 
its importance has probably been greatly overemphasized, as its dam- 
age is usually negligible in most localities. 
PINE-Tie Morus 
The pine-tip moths belonging to the genus Rhyacionia may cause 
considerable damage to new leaders and shoots of young pine in lo- 
calities where heavy infestation occurs, especially in plantations or 
on cut-over lands where trees are openly spaced and growing on 
sunny exposures. Trees from seedling size up to a height of about. 
25 feet are the most susceptible to injury. The small moths are yel- 
low, gray, or reddish brown. They lay their eggs on the pine needles, 
and the young caterpillars start feeding at the tips of shoots, bur- 
rowing into the buds and down into the new growth. Their work is 
characterized by a resinous exudation at the point of attack, but they 
do not form a pitch nodule on the stem. Though trees are seldom 
killed, they are often deformed or forked, and height growth is re- 
tarded. Several species have been described from the Western States, 
where they normally work on the tips of young forest trees. Two 
species are particularly destructive in the pine plantations of the 
Nebraska National Forest. 
Rhyacionia frustrana Busck (28, 38, 83) causes a limited amount 
of damage to seedlings and saplings in its native range in the Black 
Hills, the Lake States, and northwestern Nebraska but has done se- 
rious damage where introduced in the isolated pine plantations of 
the Nebraska National Forest. In the ponderosa pine plantations 
of this forest about 90 percent of the leaders have been injured an- 
nually for many years by this tip moth. The adult moths are small, 
with a wing spread of about one-half inch. The front wings are 
mottled with yellowish gray and reddish brown. The larvae are 
yellowish and when full grown are nearly a half inch long. A single 
generation occurs in the Black Hills, the moths flying late in May 
and early in June to lay their eggs on the pine needles, and the larvae 
feeding during June and July. In Nebraska two generations de- 
velop annually, the moths flying in April and May and again late in 
June and early in July. The winter is passed in the pupal stage in 
cocoons spun by the larvae in the litter or soil. 
Rhyacionia neomexicana Dyar has caused considerable injury to 
ponderosa pine seedlings and saplings at various places in the South- 
west and is becoming a serious pest at present in the Nebraska Na- 
tional Forest plantations. It is known to occur in New Mexico, 
Arizona, southern and eastern Colorado, the Black Hills, and Ne- 
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