The polyphemus moth occurs throughout the United States, southern Canada, and south into Mexico. The larva (Photo 1) feeds on the foliage of many species of trees, including oak, maple, basswood, beech, butternut, walnut, birch, yellow-poplar, sassafras, ash, willow, elm, and sycamore.
The adult is a large moth (Photo 3) with a wingspan of 100-150 mm. Color is somewhat variable but is commonly reddish brown. Each front wing has an oval transparent spot edged with yellowish white; each hind wing has an eyespot ringed with yellowish white and set in a larger blue-black area of the wing. Near the margin of each wing there is a black line with a light border outside.
Moths mate (Photo 4) and females lay eggs singly, and seemingly at random, on the lower surface of leaves. The egg (Photo 5) is flat and round, about 1.25 mm thick, 3 mm in diameter, and cream to light tan on top with a brown margin.
Larvae (Photo 6) are solitary feeders throughout development. Spring-brood larvae are present through June, usually becoming fully grown by about mid-July in the Auburn vicinity. The full-grown larva (Photo 1 and Photo 6) is about 75 mm long. The head is reddish brown and the body yellowish green or apple green. Each body segment bears six yellowish to orange tubercles armed with bristles. Spiracles are red to orange. Along the side of each of abdominal segments 2-7, there is a conspicuous slanted to nearly vertical yellow line. The last abdominal segment bears purplish-brown horizontal lines that form a V design at the rear. Full-grown larvae cease feeding and construct characteristic cocoons wrapped in leaves on the tree (Photo 7) and pupate. In the Auburn vicinity, new adults usually emerge in late July and early August and begin a second generation. Second-generation larvae complete development by fall and construct cocoons in which they overwinter as pupae.
The polyphemus female tends to scatter eggs rather than concentrate them in masses on individual leaves; consequently, the number of caterpillars on any one tree is usually low. As a result, large trees with abundant foliage seldom lose sufficient foliage to injure the tree, but its aesthetic value in the urban landscape may be reduced. However, among seedlings and small trees where foliage is limited, one to a few of these large, voracious feeders can cause serious defoliation. Loss of leaves in this circumstance can affect tree growth, form, and survival.
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All photos courtesy of Lacy L. Hyche