418 MISC. PUBLICATION 657, U. S. DEPT. OF AGRICULTURE 
attain full growth by early June, and the moths are active during the 
latter part of June. The eastern tent caterpillar is usually abundant 
each year in one or more localities and often over a considerable ter- 
ritory. The tents are more or less common in the forks of branches 
on wild cherry and apple during May and June. During periods of 
abundance trees are often completely defoliated and undoubtedly 
materially weakened, though rarely killed. 
Where spraying programs are not feasible, much can be done in 
the way of protecting shade and roadside trees and in reducing the 
population of the eastern tent caterpillar by the following methods 
carried out cooperatively: 
1. Cut and burn all wild cherry, and seedling and worthless apple 
trees along roadsides, fence rows, and on land of scenic and recrea- 
tional value. This not only aids materially in preventing outbreaks 
of the eastern tent caterpillar but also reduces the hazard of injury by 
many other common insect pests. 
2. Collect and destroy the egg masses during the winter months 
when they can be seen easily on the twigs. Small remunerations are 
sometimes offered to school children, 4-H Club members, and Boy and 
Girl Scouts for collecting the egg masses. 7 
3. In the spring after the eggs have hatched and as soon as the 
small caterpillars have formed tents large enough to be seen easily, 
they can be sprayed with DDT, with effective results. 
The moth of the forest tent caterpillar (M/alacosoma disstria Hbn.) 
is ight buff brown with a wing expanse from 1 to 114 inches, the 
forewings having two darker oblique lines near the middle (fig. 
85, B,a). The egg mass contains from 100 to 350 eggs cemented to- 
gether, and entirely encircling a twig (fig. 85, B, 6). The mass is 
cylindrical or ringlke in shape, ending squarely at each end, and is 
coated with a dark-colored, gluelike substance. The full-grown larva 
is about 2 inches long. The head and body generally are pale bluish, 
and there is a row of keyhole-shaped white spots along the back (fig. 
85, B,c). The cocoon of whitish silk usually is spun between leaves 
or in any type of a crevice that offers protection. 
The insect is distributed throughout the greater part of the United 
States and Canada. The foliage of ash, birch, black gum, red gum, 
sugar maple, oak, and poplar is preferred, but other deciduous forest 
and shade trees are also commonly fed upon. 
There is one generation a year. The majority of the moths issue 
during a period of about 2 weeks, from early May in the South to 
late June and July in the Northeastern States. Egg laying soon takes 
place, and hatching occurs the following spring at about the time the 
leaf buds are bursting. The caterpillars are gregarious until nearly 
full grown and do not spin a tent, but only a silken mat on the trunk 
or branch where they congregate when at rest or during their molting 
periods (fig. 86). About 5 or 6 weeks from the time of hatching each 
caterpillar surrounds itself with an oval cocoon composed of several 
layers of silk in which it transforms to the pupal stage. The moth de- 
velops and issues 10 days to 2 weeks later. 
This species probably is the most widespread defolhator of deciduous 
forest and shade trees throughout the eastern part of the United States. 
It has attracted attention since colonial days, though sometimes out- 
breaks have occurred at rather long and irregular intervals. Serious 
