is spent as a pupa in the ground. There may be two generations 
per year as far north as New England. 
Nerice bidentata Wlkr. feeds on elm in southern Ontario and 
from New England to the Lake States and Kansas. Full-grown 
larvae are bluish-green and about 30 mm. long. There are four 
white bands on the front and sides of the head, and there is a 
large forward-pointing tubercle on each of the first eight abdomi- 
nal segments, and-a pair of small ones, on the ninth. Larvae are 
present from June to September, and the winter is spent in silken 
cocoons on the ground. There are one or one and a partial second 
generations per year. 
Symmerista canicosta Franclemont [=albicosta (Hbn.)], the 
red-humped oakworm, occurs in southeastern Canada and 
throughout much of northeastern United States. Its hosts are 
various oaks, preferably white and bur, and several other decidu- 
ous trees such as basswood, sugar maple, paper birch, beech, and 
elm. An outbreak covering several thousands of acres of oak type 
occurred in Michigan in 1957 and 1958. The adult is ash gray, 
with a long, white area near the outer two-thirds of the costal 
margin of each forewing, and it has a wingspread of 37 to 50 mm. 
The full-grown larva has a rounded, orange-red head and a yel- 
lowish body that increases in width back to an orange-red en- 
largement on the eighth abdominal segment. The body is also 
marked with fine black dorsal lines (fig. 118). 
Adults appear from May to July and the female deposits her 
eggs in masses on the undersides of leaves. The larva feed gre- 
gariously at first and skeletonize the foliage. Later, they scatter 
out and feed singly, devouring entire leaves except the larger 
veins. Mature larvae move to the ground and spin cocoons in 
rolled leaves where they pupate and spend the winter. There 
appears to be one generation per year. 
Populations are usually too light to cause serious injury. Some- 
times though, they are heavy enough to cause severe defoliation 
in isolated spots. 
Symmerista albifrons (J. E. Smith) occurs in southern United 
States. Its hosts are much the same as those of the red-humped 
oakworm, a species with which it is easily confused both in ap- 
pearance and habits. At least 12,000 acres of northern hardwoods 
were defoliated in Upper Michigan and Wisconsin during an out- 
break in 1961. There are two generations per year. The orange- 
humped mapleworm, S. leucitys Franclemont, occurs in the 
F-519531 
FIGURE 118—Larvae of Symmer- 
ista canicosta, the red-humped 
oakworm. 
