single nest. Ugly nests on the twigs and branches of young pines being grown for 
the Christmas tree trade sometimes make it impossible to sell them. 
Tetralopha asperatella Clemens, the maple webworm, occurs in southeastern 
Canada and throughout the Eastern United States. The larvae feed on the foliage of 
various hardwoods such as sugar, red, and mountain maples, oak, elm, beech, 
quaking aspen, and willow. The moth is powdery gray, with the outer half of the 
forewing somewhat lighter. Full-grown larvae range from pale yellow through 
shades of green to brown or black and are about 25 mm long. On sugar maple in 
Wisconsin, eggs are laid on leaves partly rolled by other insects. When the larvae 
hatch they feed on these leaves as skeletonizers; older larvae web together groups of 
leaves, sometimes including all of the leaves on a branch in a web (fig. 69). 
Heaviest infestations apparently occur in the more open portions of the crowns of 
trees growing in the most exposed positions in the stand. When the larvae become 
full grown, they leave the nest and drop to the ground on strands of silk. The winter 
iS spent as a prepupa in a cocoon spun in the duff on the ground. There appears to 
be only one generation per year (483). 
F-519532 
Figure 69.—Characteristic nest of Tetralopha asperatella 
on oak. 
This species had never been considered economically important until it was 
shown to be a major factor leading to the development of “maple blight,” a 
condition responsible for killing thousands of valuable sugar maples in Wisconsin 
during the late 1950's. 
Other species of Tetralopha that occur in the Eastern United States are T. militella 
Zeller feeding on sycamore; and 7. melanogrammos Zeller, on sweetgum. Another 
species identified only as being near T. asperatella is sometimes abundant locally 
on beech in New England. The larva is yellowish green and has two pale, brownish 
stripes running down the back. 
Subfamily Phycitinae 
The subfamily Phycitinae contains many important tree-infesting species. The 
larvae differ considerably in their habits. Some feed in rolled or folded leaves: some 
180 
