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Pale-winged Gray

Iridopsis ephyraria[3]

The pale-winged gray (Iridopsis ephyraria) is a native moth whose inchworm caterpillars feed on many broadleaf trees and shrubs and on conifers. It has only recently been seen damaging eastern hemlock: outbreaks start on understory trees and work up into the crowns, and at high numbers the caterpillars can strip and kill a tree within 2 years.[2][1]

Group
Insect
Order
Lepidoptera
Family
Geometridae
US records
27 states
Sources
3 cited
Updated
2026-11-09
Pale-winged gray moth, a pale gray moth with dark wavy lines across its wings
Pale-winged gray moth, a pale gray moth with dark wavy lines across its wings. (c) Louis Imbeau, some rights reserved (CC BY) — via iNaturalist, CC BY 4.0
On this page
  1. Identification
  2. Look-alikes
  3. Where it lives
  4. Biology
  5. Damage and signs
  6. Health risk
  7. Control
  8. Related profiles
  9. Common questions
  10. Sources

How to identify it

  • Young caterpillars, which hatch in June, have a dark gray body, a rusty head and a yellowish rear tip.[2]
  • Older caterpillars are gray-brown to light brown with very fine, vague markings. There is a black spot on the side just ahead of mid-body, often with a small white patch in front of it, and four small black spots along the rear half of the body.[2]
  • The USDA Forest Service guide describes the caterpillar as green, gray, brown or rust, with a wart on the side of the second abdominal segment that is often dark, and often a dark spot behind each breathing hole on the abdomen.[1]
  • There is a modest hump over the eighth abdominal segment, and the head is abruptly flattened in front, with the face lighter than the top and sides. Full grown the caterpillar is 22 to 26 millimeters (about 1 inch) long.[1][2]
  • The moths fly at night and are very hard to see when resting on tree trunks, because their coloring blends in with moss and lichen.[2]

Look-alikes

Look-alikeHow to tell them apart
Bent-line gray (Iridopsis larvaria)Its caterpillar resembles the pale-winged gray's in many respects. Unlike other Iridopsis, the pale-winged gray spends the winter as an egg.[1]

Where it lives

It ranges from Nova Scotia to southeastern Alberta and south to Georgia, Alabama (in the mountains) and Texas, in forests and woodlands. Its hosts and range suggest it is mainly a species of eastern hardwood forests.[2][1]

US map: public records from 27 states since 1990 (GBIF).

Biology and life cycle

Hosts include apple, ash, birch, cherry, chokecherry, cranberry, currant and gooseberry, maple, oak, pear, viburnum, elm and willow, as well as balsam fir, eastern hemlock and other conifers.[2][1]

There is one generation a year. Unlike other Iridopsis, it overwinters as an egg on tree bark. The eggs are tiny (about 0.68 millimeter), oval with one flat end, and turn from greenish to rusty.[2][1]

In July the grown caterpillars drop to the ground and pupate just under the leaf litter, down to about 10 centimeters (4 inches) in the soil. The brown pupae are 10 to 11 millimeters long.[2]

Moths emerge 13 to 20 days later and are active from July to mid-August. Females lay their eggs on bark rather than on the foliage.[2]

In Connecticut grown caterpillars are found in June and July and the species is locally common; in Maryland they mature as early as May and it is uncommon.[1]

Damage and signs

  • On eastern hemlock, young caterpillars feed on new shoots and older ones eat older needles. Look for missing or red needles, especially on understory trees or the lower branches of larger trees.[2]
  • In the first year of an outbreak the caterpillars feed on understory trees. Over the next few years, as the understory is stripped, they move up into the crowns of mature trees. When populations are high they can completely defoliate and kill a tree within 2 years.[2]

Health risk

The sources describe it only as a tree-feeding caterpillar and a night-flying moth; they mention no harm to people.[2][1]

Control

Prevention

Neither source recommends a specific control. Natural Resources Canada's early signs to watch for are missing or red needles on understory hemlocks and on the lower branches of larger trees, where outbreaks begin.[2]

Common questions

Why are the young hemlocks under my big hemlocks turning red and bare?
One possible cause is the pale-winged gray. Its outbreaks start with caterpillars feeding on understory trees, leaving missing or red needles, before they move up into the crowns of larger trees.[2]
Where do pale-winged gray caterpillars go after feeding?
In July the grown caterpillars drop to the ground and pupate under the leaf litter. The moths appear 13 to 20 days later and lay eggs on the bark, where the eggs spend the winter.[2]

Sources

  1. USDA Forest Service, Forest Health Technology Enterprise Team, “Geometroid Caterpillars of Northeastern and Appalachian Forests, FHTET-2001-10 (D. L. Wagner, D. C. Ferguson, T. L. McCabe and R. C. Reardon, September 2001; scanned copy).” archive.org/details/geometroidcaterp00wagn (accessed 2026-11-09)
  2. Natural Resources Canada, Canadian Forest Service, “Pale winged grey, Trees, insects and diseases of Canada's forests.” tidcf.nrcan.gc.ca/en/insects/factsheet/1000141 (accessed 2026-11-09)
  3. iNaturalist, “Iridopsis ephyraria taxon page (order and family).” www.inaturalist.org/taxa/222285 (accessed 2026-11-09)

Updated 2026-11-09. Built from sourced records. Spot an error? Tell us.