Adults are present during the spring and summer. Egg laying begins in early 
June, and eggs are deposited in masses on the undersides of leaves. The larvae feed 
in colonies until almost full grown (fig. 92). They are often found in masses on the 
trunk and larger limbs where they congregate to molt. Later, they return to the 
foliage to continue their feeding. Full-grown larvae drop to the ground and wander 
about searching for pupation sites. At this time they are often found in large 
numbers along the foundation walls of houses. Pupation occurs in the soil and there 
are one or two generations per year, depending on locality (532). 
Courtesy Ill. Nat. Hist. Surv. 
Figure 92.—Colony of larvae of the walnut caterpillar, 
Datana integerrima. 
The walnut caterpillar is frequently a serious pest of walnut. Trees heavily 
defoliated 2 or more years in succession are seriously injured or killed. Isolated 
trees or trees growing in small groups are especially subject to heavy attack. Losses 
have been particularly severe in the Central States (39/). 
Datana major Grote & Robinson feeds on azalea and apple and various shrubs 
from the East Coast to Illinois. Full-grown larvae have mahogany-red heads, 
cervical shields, and legs. Their bodies are marked with longitudinal, yellow lines 
broken with black, giving them a finely spotted appearance. 
Hyperaeschra stragula (Grote) has been recorded from southern Canada and the 
Northern States, where it feeds on willow and quaking aspen. Full-grown larvae are 
about 37 mm long. The head 1s flattened in front and slightly bilobed. The body is 
mostly pearly gray with a reddish-brown dorsal line between the head and second 
tubercle. The second and third abdominal segments each bears a conical tubercle 
directed backward, and there is a prominent, pale-rust hump on the eighth abdomi- 
nal segment. Larvae are found from June to October, and the winter is spent as 
pupae in the ground. There are one and sometimes two generations per year. 
Pheosia rimosa Packard, the false-sphinx, occurs rarely in eastern Canada and 
from coast to coast in the Northern United States. Its hosts are recorded as poplars, 
especially quaking aspen, and willow. Full-grown larvae are lead-colored with a 
218 
