76 



MISC. PUBLICATION 273, U. S. DEPT. OF AGRICULTURE 



to 1932, when 50,000 acres were involved and abont 200,000,000 feet 

 of hemlock timber destroyed. 



Although western hemlock is the preferred host, the caterpillars 

 appear in countless thousands when an outbreak occurs and feed on 

 any foliage at hand. Douglas fir, Sitka spruce, and western red 

 cedar may be heavily attacked when in mixture with hemlock; 

 also huckleberry, salal. and broadleaved forest shrubs and trees 



are frequently e a t e n. 

 In fact, when the cater- 

 jDillars are exceptionally 

 n u m e r o u s, nothing 

 green is left on the in- 

 fested areas. 



The moths are light 

 buff, with a wing ex- 

 panse of about 11/2 

 inches. The forewings 

 are marked with two 

 wavy lines and the hind 

 wings with one Avavy 

 line. They fly, mate, 

 and lay eggs late in 

 September and during 

 October. The eggs are 

 about the size of a pin- 

 head, gray green or 

 brown, and are attached 

 to the moss on the tree 

 trunks, or to twigs or 

 branches. It is in this 

 stage that the winter is 

 passed, and t h e eggs 

 h a t c h the following 

 spring. The young lar- 

 vae, which a r e about 

 o n e-f o u r t h inch in 

 length, crawl up the 

 tree trunks and start 

 feeding on the young 

 needles. The first feed- 

 ing takes place in May, June, and the early part of July and 

 is not particularly noticeable. However, from the middle of July 

 to October the feeding of the caterpillars causes a heavily infested 

 forest to turn yellowish red and then brown, as though scorched by 

 fire. Late in summer the caterpillars feed on the foliage, clip off 

 small twigs, crawl over the trunks, cling to shrubs, and drop by 

 silken webs from the trees to the ground. These silken webs may 

 become so abundant that the whole forest looks and feels like one 

 big cobweb. When full grown, the caterpillars are about li/^ inches 

 long, green to brown, with diamond-shaped markings on the back. 

 They drop to the ground in August and September and secrete them- 

 selves in protected places, such as crevices of the bark or under 

 debris on the ground, and there transform to pupae. 



FiGUKE 35. — The hemlock looper {Ellopia fiscelkiria var. 

 lugiihrosa) : A, Larvae on branch; B, pupae; C, adult 

 moth. Natural size. 



