INSECT ENEMIES OF WESTERN FORESTS 71 



The caterpillars of this tussock moth are striking looking creatures, 

 decorated with brightly colored tufts of hairs. When full grown 

 they are from three -fourths to 1 inch in length, Avith gray or light- 

 brown bodies and black, shiny heads. There are two long brushes 

 or pencils of black hairs fully one-fourth inch in length, suggesting 

 horns, directly behind the head, and a similar but longer tuft at the 

 posterior end of the body. On the upper side of the first four and 

 the last abdominal segments are dense, light-brown or cream-colored 

 tufts of hairs about one-sixteenth of an inch in length, and numerous 

 red spots. Along the sides of the body are somewhat broken, nar- 

 row, orange stripes, wdiile the lower side of the body is nearly naked, 

 wdth the prolegs only sparsely covered with hairs. 



The adult moths are far more ordinary looking than their hand- 

 some larvae, being a dull brownish gray. The males are about 

 one-half inch long and have a wing expanse of nearly an inch. The 

 wingless females are about one-half the length of the males. 



Normally there appears to be one generation a year. The small 

 caterpillars hatch from the eggs and commence feeding on the new 

 foliage early in spring, but it is not until about the 1st of August 

 that the defoliation is likely to become severe enough to be noticeable 

 at a distance. The larvae reach full growth early in August and then 

 pupate. The moths appear the latter part of August and mate soon 

 after emergence. The winter is passed in the egg stage. 



One of the most important parasites is a tachinid fly, somewhat 

 larger and more hairy than the ordinary housefly. The larvae of this 

 fly live in the caterpillars and emerge after these have formed their 

 cocoons. A very small wasplike insect, Trichogramma minutum 

 Riley, attacks the eggs and destroys a high percentage of them. 

 There are at least five other wasplike insects that are important 

 parasites of the larvae. 



Determination of the feasibility of artificial control of this de- 

 foliator involves not only the consideration of effective methods but 

 the cost of applying them. The spreading of arsenical dust by air- 

 plane probably would offer the best chance of success of any method, 

 but at this time it cannot be recommended on account of risk and 

 cost. Such methods as collecting and destroying the egg masses 

 during the winter months, jarring the caterpillars from the trees, 

 banding the trees to prevent ascent of the caterpillars, and powder 

 spraying, are applicable to the control of this insect only under park 

 or shade-tree conditions. 



Other closely related species of tussock moths w^hich feed on forest 

 trees in the Western States include : 



Species Host and distribution 



Hemerocampa oslari Barnes White fir. California and Colorado. 



Hemerocampa vetusta Bdv Oak, poplar, willow, and various other 



broadleaved trees. Pacific coast. 



Hemerocampa gulosa Hy. Edw Oak. California Sierras. 



Hemerocampa leucostigma A.and S. Poplar and other broadleaved trees. In 



the East, and west into Colorado and 

 British Cohimbia. 



Notolophus antiqua L Alder, ash, aspen, larch, oak, pine, poplar, 



willow, and other broadleaved trees and 

 shrubs. From California to British Co- 

 lumbia and east to Montana, 



