Courtesy Conn. Agric. Exp. Stn. 
Figure 98.—Larva of the pale tussock 
moth, Halysidota tessellaris. 
The sycamore tussock moth, H. harrisii Walsh, feeds on sycamore and London 
plane trees, and it probably occurs wherever sycamore grows in this country. Adults 
are indistinguishable from those of the pale tussock moth, and the larvae of the two 
species differ only in color. Larvae of this species have yellowish bodies clothed in 
whitish to yellow hairs, and the long hair pencils are orange. Infestations are often 
heavy on shade and ornamental sycamore in the Northeast. 
The fall webworm, Hyphantria cunea (Drury), occurs throughout the United 
States and southern Canada. Its hosts include more than 100 species of forest and 
shade trees. The adult has a wingspread of 30 to 42 mm, and the bases of the front 
legs are orange or bright yellow. In the southern part of its range, the moth is white, 
usually with dark spots on the wings. In the North, particularly in eastern Canada, 
it is nearly always pure white and was formerly referred to as H. textor Harris. Full- 
grown larvae are usually pale yellowish or greenish, with a broad, dusky stripe 
down the back and a yellowish stripe down each side. They are about 25 mm long. 
Their bodies are covered with long, silky, gray hairs arising in tufts from orange- 
yellow or black tubercles. Head color varies from red to black. The larvae of H. 
textor are dark. 
Adults appear mostly from May to July and deposit their eggs in hair-covered 
masses of several hundred each, usually on the undersides of leaves. Newly 
emerged larvae immediately begin to spin a silken web over the foliage on which 
they feed; as they grow, they enlarge the web to enclose more and more foliage (fig. 
99). On heavily infested trees several branches may be enclosed in webs. Small 
trees are often enclosed entirely. The larvae are gregarious until the last instar. 
During the early stages, they feed on the upper surface of the leaves; later they 
devour entire leaves except the larger veins and midribs. As they approach maturity, 
some larvae leave the web and feed individually. Pupation occurs in thin cocoons 
usually spun in the duff or just beneath the surface of the soil. There are one to four 
generations per year, depending on location. 
The fall webworm is ordinarily of no great importance as a forest pest since it 
usually attacks understory weed species of no economic value. Outbreaks may 
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