414 MISC. PUBLICATION 657, U. S. DEPT. OF AGRICULTURE 
because their silk checks the growth of the leaves in the spring and 
the larvae become serious defoliators. Moreover, the larvae are a 
serious menace to public health because of the irritation or rash 
caused by the poisonous barbed hairs when they come in contact with 
the human skin. 
NaruraL Enemies.—The introduced parasites Carcelia laxifrons 
Vill., Compsilura concinnata, Sturmia nidicola Towns., Apanteles lac- 
teicolor, and Meteorus versicolor Wesm., are effective enemies of this 
pest, as is also the introduced predator Calosoma sycophanta. A 
fungus disease, Hntomophthora aulicae Reich, which attacks the lar- 
vae is an effective enemy. Low winter temperature often plays an 
important part in the control of this pest. Burgess and Crossman 
(73) discuss the natural control of this pest. 
ControL.—Spraying with an arsenical or DDT (p. 53) is the most 
effective method of artificial control in the forest. See caution on 
p. 28). Correct orchard practice will control this insect in the orchard. 
In residential areas, on farms, and along roadsides and fence rows, 
the method used is to cut off and destroy the winter webs before the 
larvae begin to emerge in April. 
Fence rows, neglected orchards, and waste land are ideal breeding 
places for this and other insect pests, so it is advisable to eliminate all 
worthless apple, pear, wild black and choke cherries, and other fa- 
vored food plants that are of little or no value. 
The Satin Moth 
The satin moth Sti/pnotia salicis (i.) (fig. 84) has a wing expanse 
of from 11% to 2 inches and is clear white with a satin luster. The 
head, thorax, and abdomen are black but are so densely clothed with 
long, satiny, white hairs as to appear white. The eggs are deposited 
on leaves, branches, and trunks of trees or on other surfaces in masses 
ranging from 100 to 400 each, although 1 female may deposit as many 
as 1,000 eggs. The masses, roughly oval in shape and about 5¢ inch 
long, are covered with a glistening white secretion. On hatching, the 
larva feeds during two instars, then seeks a crevice or depression on 
some part of the tree, sometimes making an excavation by chewing the 
bark, and spins a cocoonlike hibernaculum in which it spends the 
winter. 
Feeding is continued the next spring. The full-grown larva is 134 
to 2 inches long, the head is black with a bluish tinge and sparsely 
clothed with short hairs, the body blackish on the dorsum with a 
broken row of large white blotches down the middle and a narrow 
broken white subdorsal line on each side. The sides of the body are 
mottled with black and white, and each segment has a transverse row 
of reddish-brown tubercles bearing yellowish-brown hairs. The pupa 
is about 1 inch long, shining black, and is clothed with golden and 
whitish hairs. The cocoon may be spun in the leaves, on the twigs, or 
on other objects, and consists of a loosely woven structure of silk (Bur- 
gess and Crossman, 72). 
DistrrisutTion.—The satin moth is widely distributed throughout 
Europe and Asia, and was first discovered in Massachusetts in June 
1920 near the Malden-Medford city line, and in July 1920 at New 
Westminister, British Columbia. By 1937 it had dispersed into all 
