moth damage (64). A reduction in the proportion of favored host 
species also decreases the chances of infestation and limits the 
degree of population build-up (532). 
Insecticidal spraying by aircraft has been most widely used 
in gypsy moth control. Attempts to secure control by spraying 
an infested stand with the nuclear-polyhedral virus, Borrelina- 
virus reprimens appeared to be successful (617). Spraying with 
the microbial insecticide, Bacillus thuringiensis thuringiensis 
Berliner (455) has given promising results. Other promising 
methods of control include male sterilization by gamma irradia- 
tion (300), sterilization through the use of chemo-sterilants 
(146), and the use of natural and synthetic sex attractants. The 
natural female attractant known as gyplure has been isolated, 
identified, and synthesized (397). 
The satin moth, Stilpnotia salicis (L.) (fig. 124), an introduced 
species first discovered in North America near Boston, Mass., in 
1920 (120) and in British Columbia during the same year, now 
occurs throughout most of New England and in the Maritime 
Provinces of eastern North America. In the West, it has spread 
southward through western Washington into Northwestern Ore- 
gon. The larvae feed on most species of poplar and willow. Adults 
of both sexes are pure white with a satiny color and have a wing- 
spread of 37 to 50 mm. The head, thorax, and abdomen are black 
but are so densely clothed with long, satiny-white hairs they 
appear white. Full-grown larvae are about 34 mm. long. The 
head is black with a bluish tinge. The body is blackish on top with 
a row of large white blotches down the middle and a narrow 
broken line along each side. There is also a transverse row of 
reddish-brown tubercles on the top of each body segment, each 
bearing a tuft of yellowish-brown hairs. 
Winter is spent in the larval stage. Feeding is resumed in April 
in New England. Young larvae feed only on the leaf surface, 
most often on the underside. Partly grown larvae eat small, ir- 
regular holes in the leaf, and full-grown larvae devour the entire 
leaf except the large veins. Feeding is completed by June. Pupa- 
tion occurs in loosely woven cocoons of silk spun in the leaves or 
on twigs or other objects. Adults appear in late June and early 
July. Mostly in July, eggs are deposited on leaves, branches, and 
trunks of trees or on other surfaces in masses of 100 to 400 eggs 
each. Each mass is oval, about 9 mm. long, and covered with a 
glistening white secretion. Hatching occurs in about two weeks. 
Newly-hatched larvae feed for 5 to 6 days and then spin small 
webs in which they molt to the second instar. These larvae then 
feed again for 5 to 6 days. Then they craw] to limbs or the trunk 
and spin hibernaculae in bark crevices or under loose bark where 
they remain until the following spring (123). 
The satin moth is not very important as a forest insect in the 
Eastern States, although heavy infestations are occasionally re- 
ported. From time to time, it seriously defoliates poplars in orna- 
mental plantings. Introduced parasites are generally credited 
with holding populations to harmless levels (205) with some as- 
sistance from low winter temperatures, disease, and birds. The 
hymenopteron, Apanteles solitarius (Ratz.), appears to be the 
most effective parasite; however, the dipteron, Compsilura con- 
324 
