A large, rusty colored and strikingly patterned moth of the eastern United States, the Promethea Silkmoth seems to be in decline across much of its range; perhaps due to the introduction of a tachinid fly to control Gypsy Moth populations. Males seek females in the afternoon and early evening, with most mating occurring from 4 PM to sunset. At night, females lay rows of 4-10 eggs on the upperside of host plant leaves in a single cluster. Young caterpillars feed together while older caterpillars are solitary. Older caterpillars do not eat the leaf midvein, but cut the leaf petiole at the base so it falls to the ground, perhaps a defensive measure eliminating visual or olfactory signs of feeding. A caterpillar ready to pupate strengthens a leaf petiole with silk and then spins its cocoon inside the curled leaf. The cocoon hangs from the host plant throughout the winter.
Males and females differ. Male body is black; wings are black with tan borders, faint tan postmedian lines, and pink near the eyespots on the forewing tips. Female wings are dark brown to reddish-brown with tan borders and well-developed tan cell spots on all wings.
Resident – uncommon
The Promethea Silkmoth has one brood and flies from May through July. In Vermont all known records are from June. Extreme dates: 25 May 1991 in Enosburg (J. Hedbor), 22 August 1991 in Burlington (R. Kim).
Distribution and Habitat
Though this moth was only found in the northern part of Vermont during our survey, this does not mean its range does not extend further south in our state. In fact, our lack of records for the Promethea Silkmoth probably has more to do with our primary attention being focused on butterflies rather than nocturnal insects. Their preferred habitat is deciduous woodlands and caterpillars feed on a broad range of plants including Spicebush (Lindera benzoin), Sassafras (Sassafras albidum), White Ash (Fraxinus americana), Lilac (Syringa vulgaris), and many others. Adults do not feed.
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