INSECT ENEMIES OF WESTERN FORESTS 



79 



The spruce hudworm, {nar?nologa) Cacoecia fumifer ana Clem. (25, 

 82) (fig. 38) , is one of the most destructive members of this group. In 

 the Northeast, in Canada, the Lake States, and the northern Rocky 

 Mountain region it has caused widespread destruction of spruce, 

 balsam firs, and Doughis fir. There are many records of budworm 

 epidemics in the Northeast in which enormous numbers of spruces 

 and balsams have been destroyed. It was not until 1922, however, 

 when two outbreaks were recorded in widely separated sections of 



Figure 38. — The spruce budworm {Cacoecia fumiferana) : A, Eggs on under side of fir 

 needle ; B, half-grown caterpillar ; C, full-grown caterpillars ; Z>, pupae ; E, fir twig 

 with pupa attached ; F, defoliated fir twig with empty pupal cases ; G, adult moths. 

 All natural size. (Evenden.) 



Idaho, that it was recognized as an important enemy in western 

 forests. The following season it was found that a budworm epi- 

 demic had been present for several years in the southwestern corner 

 of Yellowstone National Park and the adjacent Targhee National 

 Forest, and in the next few seasons outbreaks were reported from 

 many Western States. In some areas these outbreaks reached alarm- 

 ing proportions and heavy timber losses followed. Though it is not 

 known whether this insect migrated or spread to the western part 

 of the United States from infested areas in the East, it is believed 

 that it is indigenous to the West and that during the last 30 or 40 

 years it has been at such a low endemic stage as to escape attention. 

 The adult spruce budworms are small, mottled, brownish moths 

 with a wing expanse of approximately 1 inch, with no distinctive 

 markings, the general color tone being a dull gray. The oval, scale- 

 like eggs, which are light green and about one-sixteenth of an inch 

 in diameter, are laid on the under side of needles, in an overlapping 

 form like shingles, with about one-third of the egg exposed. The 



