The forewings of adult magdalen underwing moths are dull tan, brown, or gray with wavy lines that mimic the random patterns of tree bark. The hindwings are bright orange with a contrasting blackish pattern: One dark band parallels the outer wing margin, which is lighter, and another blackish mark is in the center of each hindwing. Note that there are dozens of similar Catocala moths in our state, and the markings can vary greatly even within a species. So even experts can have a difficult time telling them all apart.
The caterpillars are cylindrical, with the body tapering at both ends. There are numerous thin, alternating white and black bands, with two rows of orange dots running down the back, and a row of orange dots around black spiracles down each side. A white stripe runs the length of the caterpillar below the spiracles.
Similar species: There are more than 60 species of Catocala moths in Missouri, and within these there are an additional 40 named forms and varieties.
Wingspan: 2¼–2¾ inches.
Habitat and Conservation
A moth of deciduous forests and forest borders, and wherever else the food trees grow. Adults are nocturnal and attracted to lights. By day, they rest in caves, under ledges, on trees or rocks, or among leaf litter on the ground. Caterpillars feed in tree canopies when young, then descend to the ground to pupate. They have been found within a yard of the base of small trees in fields, resting head-down on dry blades of grass. The white stripe above the feet helps them blend in with grasses.
Larvae have been known to feed on the foliage of honey locust, black locust, and leadplant, and possibly other woody members of the pea family. The adults can be attracted to sugary water brushed on a tree trunk, and therefore probably also consume the sweet liquids of nature: flower nectar, the juices of fallen ripe fruits, and so on.
The underwings (genus Catocala) used to be placed in the noctuid family (Noctuidae), alongside the owlet, dagger, miller, and dart moths, the cutworms, the armyworms, and more. But genetic research has shown they belong in the same family with tiger, lichen, and tussock moths, and a new family was created for this group: Erebidae.
Adults fly from about May and perhaps into September. All Missouri species of underwings are single-brooded, feeding in the larval stage on the foliage of trees and shrubs and overwintering in the egg stage, usually on the bark of trees. Unlike moths that overwinter as mature caterpillars or as pupae, underwings must hatch from eggs in the spring and then grow through all their larval stages and pupate before we can see any adults flying around.
Because of their bright hindwings, underwing moths are favorites of amateur entomologists and of collectors and photographers of moths and butterflies, who use a sugar solution painted on the bark of trees as bait.
The genus name is pronounced “kah-TAH-kuh-luh” and is from Greek words meaning “beautiful below” — a reference to the colorful hindwings.
The caterpillars graze on vegetation, checking the growth of their food plants, and possibly invigorating them by a form of natural pruning.
All stages provide food for predators. The bright hindwings serve to deter predators: Normally hidden beneath the drab forewings, their bright colors are suddenly exposed when the moth is disturbed, startling the predator and allowing the moth to escape.