INSECT ENEMIES OF WESTERN FORESTS 49 



nearly iy 4 inches. There are two narrow W-shaped bands extend- 

 ing across each forewing; the hind wings are dusky white. The 

 moths appear from late in July to early in September and deposit 

 eggs singly on the under side of bark scales, on trunk, or on 

 branches. The small larvae hatch in 1 to 4 weeks, depending on 

 the temperature, and spin small hibernacula under bark scales, in 

 which they overwinter. The first evidence of attack appears the 

 following spring in the form of a small quantity of larval castings 

 on the bark surface, followed by an exudation of pitch from the 

 entrance hole. The larvae feed in the cambium region and con- 

 struct irregularly shaped galleries beneath the bark. Some of these 

 are rounded cavities with short side galleries, while others extend 

 several inches around the tree. The mature larvae are about 1 

 inch long, usually light brown, occasionally with a greenish tinge, 

 and the bodies are marked with about six rows of small, dark- 

 brown dots, or tubercles. These larvae spin white papery cocoons 

 in the burrows, or sometimes in the dried-pitch mass near the 

 surface, in which pupation takes place in July. The new adults 

 leave the pupal skins in the cocoons and force their way through 

 exit holes previously prepared by the larvae but concealed by 

 flakes of bark or small webs. 



Control was attempted by spraying the infested part of the 

 stems with orthodichlorobenzene, diluted 1 to 5 with water, to 

 which a small quantity of soap and linseed oil was added. The 

 results were only partially satisfactory. Winter cutting and re- 

 moval of the most heavily infested trees in the plantations resulted 

 in a considerable reduction in the infestation. Control measures, 

 however, are still in the experimental stage. 



Dioryctria xanthoenobares Dyar is a golden-brown moth about 

 % inch long, which in the caterpillar stage attacks the twigs and 

 cones of ponderosa and knobcone pines and possibly other pines. 

 The caterpillar is pinkish and about 1 inch long when full grown. 

 It is known in California, Oregon, Washington, and Nebraska. 



Dioryctria abietella D. & S. is a gray moth about % inch long. 

 The reddish caterpillars feed in the twigs and cones of pines, firs, 

 Douglas-fir, and spruce in all the Western States. There appear to 

 be two annual generations. (See p. 22.) 



The Zimmerman pine moth (Dioryctria zimmermani (Grote)) 

 (Pinipestis) is a medium-sized light- to reddish-gray moth with 

 a wing expanse of 1 to V/ 2 inches and marked with zigzag dark 

 and lighter lines. The larvae are about % inch long when full 

 grown and range in color from a dirty white through reddish 

 yellow to green. This pine moth appears to be distributed through- 

 out the United States and attacks many species of pines. It is 

 reported by Brunner (17) as being destructive to all coniferous 

 trees, especially ponderosa pine, throughout the Pacific Northwest. 

 Brunner credits the "spike top" of mature trees and the spike top, 

 stunting, and destruction of smaller trees, to the work of this in- 

 sect. However, its importance has probably been greatly over- 

 emphasized, as its damage is usually negligible in most localities. 



The moths fly from May to September, but mostly in July. Eggs 

 are deposited on the bark near wounds, and the newly hatched 



