INSECT ENEMIES OF WESTERN FORESTS 83 



pupate ; hence their common name. As a forest pest the most im- 

 portant in this group is the pandora moth. 



The pandora moth (Coloradia pandora Blake) (fig. 33) is an 

 important defoliator of ponderosa pine in the forests of south- 

 central Oregon, of Jeffrey pine in California east of the Sierra 

 Nevada, and of lodgepole pine in central Colorado. This moth and 

 closely allied species or varieties have been reported from nearly 

 all Western States, where they feed upon various pines. 



A destructive outbreak of the pandora moth occurred on the 

 Klamath Indian Reservation of southern Oregon in 1918-25 (131). 

 Thousands of acres of ponderosa pine forest were heavily defoli- 

 ated, with an accompanying serious loss of timber. Lodgepole pine 

 was also attacked when in mixture with ponderosa. Heavily de- 

 foliated trees died after 2 or 3 years. Others were greatly reduced 

 in growth and recovered only after several years. The loss in 

 growth throughout the defoliated area mounted to several million 

 board feet. Even more serious was the bark-beetle damage that 

 followed the defoliation and increased to alarming proportions in 

 the weakened trees. Most severely injured were the pines growing 

 on loose pumice soil, where the caterpillars could easily bury them- 

 selves for protection during pupation. 



On the Arapaho National Forest in north central Colorado, an 

 epidemic during the period 1937-40 defoliated lodgepole stands 

 on an area of approximately 100,000 acres. This defoliation killed 

 more than 4,000 trees and weakened many others (161). 



Although some infestation may be found every few years, the 

 records indicate that epidemics occur at fairly regular intervals 

 of 20 to 30 years and continue in intensity for 6 to 8 years. During 

 periods of abundance feeding may be fairly heavy without serious 

 consequences. This is because the terminal buds are not eaten, and, 

 since the insect has a 2-year life cycle and most of the feeding 

 occurs in alternate years, the trees have an opportunity to recover. 

 The more vigorous trees survive the attacks, and only during 

 major outbreaks are losses likely to be heavy. 



The adults are large, heavy-bodied, grayish-brown moths, with 

 a wing expanse of 3 or 4 inches and a small dark spot near the 

 center of each wing. The base and interior margins of the hind 

 wings are clothed with pinkish hairs, which in the male shade to 

 wine color. The males have large, feathery antennae, while the 

 females have slender antennae and heavy bodies. During epidemics 

 thousands of these large moths will be seen fluttering over the 

 tree trunks and flying through the woods. The globular eggs, about 

 y 10 inch long, are laid in clusters on the trunks or branches of 

 trees or on litter on the ground. The newly hatched caterpillars 

 are about 14 inch long, with shiny black heads and black or brown- 

 ish bodies covered with short, dark hairs. When mature, the cater- 

 pillars are from brown to yellowish green and 2y 2 to 3 inches long, 

 with each segment supporting a few stout branched spines. 



The pandora moth requires 2 years to complete its life cycle. 

 Adults appear the latter part of June and in July, and the eggs 

 hatch in August. The young larvae crawl up the trees and during 

 the early molts feed in groups on the new foliage. At the end of 



