576 MISC. PUBLICATION 657, U. 8S. DEPT. OF AGRICULTURE 
This species is widely distributed over much of the eastern part of 
the United States and Canada. The larvae prefer willow as food but 
will attack poplar. They are vigorous defoliators, especially of young 
trees, and occasionally strip willows in ornamental plantings and in 
long stretches along the banks of streams. It is considered one of the 
most injurious pests of basket willow, particularly in the South, where 
there are several generations annually. There is an overlapping of 
generations, and the number of generations a year varies in the differ- 
ent climatic ranges. 
There is probably one generation a year in the northern limits of 
its habitat, two and sometimes a partial third in some New England 
localities, and as many as five in the District of Columbia. Occa- 
sionally in New England some specimens remain in a diapause for 
at least 19 or 20 months. The adults emerge in the spring, the exact 
dates depending on the climate. The females lay their eggs in pockets 
cut in the tissue of the leaves. The young larvae at first feed in close 
colonies, making small holes in the leaves. Apparently the develop- 
ment of a generation requires about 1 month under the most favor- 
able conditions. Cocoons are spun in the litter or topsoil beneath the 
trees. The winter is passed as prepupal larvae within their cocoons. 
The full-grown larva of Pteronidea odorata (Dyar) is about 5g inch 
long. The head is shining black, and the body is light green with 
three longitudinal rows of almost contiguous black spots on the back, 
but in younger larvae these rows of spots are well separated. The 
sides of the body are spotted with black, a row just beneath the 
spiracles and another near the bases of the legs being largest and most 
conspicuous. The venter has five pale yellow scent glands behind 
the abdominal legs on joints 6 to 10. The anal plate is black with a 
pair of terminal spines, and the thoracic legs are black except at the 
joints. This species occurs through the Northeast and in some years 
is abundant locally. The larvae feed on species of willow. In New 
England there may be two generations annually or one and only a 
partial second. The winter is passed as prepupal larvae in cocoons 
on the ground. The adults emerge late in May and in June. First- 
generation larvae may be found in June and July. Adults of the 
next generation emerge during the latter part of July, in August, 
and in the early part of September. Second-generation larvae are 
found in August and September. 
In addition to the species of Pteronidea already discussed, several 
others are native to the Eastern States and occasionally become 
abundant enough to attract attention, at least locally. The larvae of 
a number of species are somewhat similar in appearance. In some 
of the more common species the full-grown larva prior to molting 
into the last instar is about 5g to 34 inch in length. The head is 
brownish to blackish. The body is generally hght green with dark, 
brown to black markings, those on the back consisting of rows of dots 
or more or less broken transverse stripes. The sides of the body are 
more or less speckled but usually have a row of conspicuous spots 
irregular in shape Just below the spiracles and one or two rows near 
base of the legs. Some have the legs marked with black and others 
concolorous with the body. A few have a row of black spots on the 
venter of the abdomen between the legs. P. alnivora Roh. feeds on 
alder, P. trilineata (Nort.) on locust, P. corylus (Cress.) on hazelnut, 
