and apple in the Eastern United States and eastern Canada. Full-grown larvae are 
greenish brown with reddish-brown heads and are about 18 mm long. There is a pair 
of tubercles on the first abdominal segment; a pair of long, slender, brownish 
filaments on each side of the second and third segments; a pair of small, rusty-red 
tubercles on the eighth segment; and a broad stripe that extends from the dorsum of 
the prothorax to the first pair of filaments. Larvae are active from May to July; 
adults, from late June to August. 
The elm spanworm, Ennomos subsignarius (Hubner) (fig. 80), occurs in south- 
ern Ontario and throughout the Eastern United States, west to Wisconsin, Colo- 
rado, and Texas. Its preferred hosts are hickory, oak, red maple, and ash but it 
attacks a large number of other hardwoods (208). About 100 years ago, it was best 
known as a shade tree pest in the larger cities of the Eastern United States (56/). It 
also has been a predominant forest pest with widespread severe outbreaks occurring 
in the southern Appalachians and Connecticut (395, 653). 
The adult is a powdery white moth with a wingspread of 30 to 37 mm. Larval 
color is related to population density (334). Full-grown larvae in outbreak areas are 
usually dull, slate black except for rusty head capsules; a small proportion of the 
larvae may be light green with yellow head capsules. When populations are low, 
there is a higher proportion of the lighter colored larvae. They are about 50 mm 
long. 
Winter is spent in the egg stage. Hatching begins in late April in the South. 
Farther north, it may not start until late May or early June. Young larvae feed on the 
lower surfaces of leaves and produce a typical shothole effect. Older ones eat the 
entire leaf with the exception of the midrib and petiole. To pupate, mature larvae 
spin coarse, netlike cocoons of silken threads, often on partly eaten leaves. In 
completely defoliated stands, cocoons may be spun on exposed branch tips, in leaf 
axils, in bark crevices, or stumps of undergrowth. 
The elm spanworm is capable of completely defoliating large areas of mixed 
hardwood forests during outbreaks. Between outbreaks, populations often exist at 
very low levels. A number of insect parasites and predators were found in fairly 
large numbers during the latter stages of some of the outbreaks and probably helped 
in bringing them to an end. The hymenopteran 7elenomus droozi Muesebeck 
parasitized and destroyed over 80 percent of the eggs in certain areas (209, 336, 
337, S95). In Connecticut, Ooencyrtus ennomophagus Yoshimoto, a par- 
thenogenetic egg parasite with more than one generation per year, ended an 
outbreak in about 2 years (654). The predacious beetle Calosoma scrutator (F.), a 
voracious feeder on lepidopterous larvae, was also abundant in outbreak areas. 
Ennomos magnarius Guenee, the notched-wing geometer, is widely distributed 
in southern Canada and the Northern States. It feeds on many species of hardwoods 
such as white ash, basswood, maple, quaking aspen, paper birch, beech, willow, 
and elm. The adult is yellowish and has a wingspread of about 60 mm. The 
forewing has a reddish tinge, is thickly flecked with brown dots, has a conspicuous 
lobe near the middle, and is shaded with brown on the outer margin. Mature larvae 
are about 50 mm long and yellowish green to dark brown or twiglike. Reddish areas 
occur on the tops of segments two and five and on the venter of segment three. 
Adults deposit oblong eggs in long, single strings during August and September. 
and winter is spent in the egg stage. Hatching begins in May, and larvae are present 
from May to July or August. This species is sometimes fairly abundant but is 
seldom of economic importance. 
196 
