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



beneficial insect, and during the following season it was practically 

 impossible to find a living caterpillar or butterfly within the de- 

 foliated areas. Before natural control becomes effective, however, 

 tremendous loss of timber may occur. 



In the future, artificial control by airplane dusting may prove 

 useful in protecting the forests from heavy defoliation during the 

 peak of the outbreak and until the defoliator is brought under 

 control b}' natural means. Even if only 50 percent of the foliage 

 of a tree could be saved by such a method it probably would be 

 sufficient to prevent its death. 



The Pandora moth {C oloradm pandora Blake) {68) (fig. 29) is 

 an important defoliator of ponderosa pine in the forests of central 

 and southern Oregon and in California east of the Sierra Nevada. 

 This moth and closely related species and varieties have been re- 

 ]3orted from practically all Western States, where they feed upon 

 various pines. The preferred hosts of the pandora moth are pon- 

 derosa and Jeffrey pines, though lodgepole pine may also be attacked 

 during epidemics when in mixture with one of the preferred species. 

 Though distributed over a wide area, it is only in pine forests grow- 

 ing on loose pumice soil, where the caterpillars can easily bury 

 themselves for pupation, that serious damage has occurred. 



The most recent destructive outbreak occurred on the Klamath 

 Indian Reservation of southern Oregon from 1918 to 1925. Thou- 

 sands of acres of ponderosa pine forest were heavily defoliated, with 

 an accompanying serious loss of timber. Heavily defoliated trees 

 were unable to recover and died after 2 or 3 years as a direct result 

 of the injury. Others were greatly reduced in growth and re- 

 covered only after a period of several 3^ears. The loss in growth 

 throughout the defoliated area amounted to several million board 

 feet. Even more serious was the bark-beetle damage which fol- 

 lowed the defoliation and increased to alarming proportions in the 

 weakened trees. 



AAliile some infestation may be found every few 3^ears, the records 

 indicate that epidemics occur at fairly regular intervals of 20 to 

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

 periods of abundance fairly heavy feeding may occur without serious 

 consequences. This is due to the fact that the terminal buds are 

 not eaten, and since the insect has a 2-year life cycle and the larvae 

 feed only in alternate years, the trees have an opportunity to re- 

 cover. For this reason the more vigorous trees survive the attacks, 

 and only during the major outbreaks are heavy losses likely to 

 be sustained. 



The adults are large, heavy-bocliecl, 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 eggs, which are globular in 

 shape ancl about one-tenth of an inch in length, are laid in clusters 

 on the trunks or branches of trees or on litter on the ground. The 



