INSECT ENEMIES OF EASTERN FORESTS 497 
sisella (fig. 119). When the larvae are disturbed they spin down on 
silken threads. The cocoons in which the pupae pass the winter are 
spun on fallen leaves or debris on the ground and sometimes on the 
trunks of trees (fig. 120). Occasional outbreaks cause considerable 
concern, particularly to owners of large country estates. It some- 
times becomes necessary to practice artificial control to prevent severe 
skeletonizing of the oak foliage. Outbreaks were recorded in Essex 
County, Mass., in 1929 and again in 1934. This insect can be controlled 
by the same measures as recommended for B. canadensisella. 
Famity COSSIDAE 
The moths of the Cossidae have rather heavy spindle-shaped bodies, 
and narrow, strong wings. They are nocturnal fliers and deposit their 
eggs on the bark of trees or within the tunnels from which they have 
emerged. The larvae are borers in 
forest, shade, and fruit trees, mak- 
ing large galleries in the wood and 
causing serious injury. 
The adult of the carpenter worm 
(Prionoxystus robiniae (Peck) ) is 
a grayish, stout-bodied moth. The 
female has a wing expanse of 3 
inches, while the male is somewhat 
smaller. The forewings are mot- 
tled and slightly translucent. The 
hind wings of the female are smoky, 
and those of the male are yellowish 
to orange with base and margins 
blackish. The eggs, numbering 
from 300 to 400 per female, are dark 
brown and oval. he larvae are 2 
to 8 inches long when full grown 
and are reddish white with a brown 
head. The brownish pupa _ is 
formed in a cell in the wood, but it | 
- FieurRE 120.—Cocoons of the oak 
wriggles to the surface so that a skeletonizer formed beneath loose 
part of it is projecting when the bark. 
moth emerges. 
This species is widely distributed throughout the United States and 
southeastern Canada. It attacks green ash, elm, locust, maple, poplar, 
oak, and other hardwoods. The moths emerge in June and July, and 
the females deposit their eggs in crevices of bark or near wounds. The 
young larvae bore through the bark and into the sapwood and heart- 
wood of the trunk and branches of the tree, and then tunnel more or 
less vertically (fig. 121). It is believed 3 to 4 years are required to 
complete the life cycle. The large burrows, up to 1% inch in diameter, 
cause serious deformities and also permit the entrance to the heart- 
wood of moisture and destructive fungi (fig. 122). Use the control 
measures recommended on page 498 for P. macmurtret. 
The little carpenter worm (Prionoxystus macmurtrei (Guer.)) is 
very similar to P. robiniae and is often confused with it, especially in 
the larval stage. Though the infestations are usually very local, it 
