Ctenucha virginica

Ctenucha virginica

Family: Erebidae

Virginia Ctenucha (Ctenucha virginica) is a colorful, medium-sized tiger moth of moist meadows, grassy fields, roadsides, and open woodland edges. Its dark gray-brown wings, metallic blue body, and yellow-orange head and collar create a bold, wasp-like appearance. Unlike many moths, adults are often active during the day and may be seen flying low through vegetation or visiting flowers.

Virginia Ctenucha is the largest of the North American wasp moths. It is especially characteristic of northern and northeastern North America and is widespread in Minnesota and the Upper Midwest. Its combination of broad dark wings, iridescent blue body, and orange head usually makes a clear adult identifiable in the field.

For representative images and visual context, see the page: Virginia Ctenucha in the Gallery section.

Description

Ctenucha virginica is generally recognized by:

• Overall form: robust, broad-winged wasp moth with a compact body and wings held roof-like over the abdomen at rest
• Size: approximately 40–50 mm, or about 1.6–2 inches, in wingspan
• Color pattern: dark gray-brown wings contrasting with a metallic blue-black body and a bright yellow-orange head and collar
• Head: yellow-orange to orange, strongly contrasting with the dark wings and thorax
• Antennae: black and conspicuously comb-like; the branches are especially prominent in males
• Thorax: black with metallic blue iridescence and a yellow-orange collar that broadens toward the shoulders
• Abdomen: dark metallic blue, most visible when the wings are spread or viewed from the side
• Forewings: broad and dark gray-brown, sometimes showing a subtle bluish sheen near the base
• Hindwings: smaller and opaque black; usually hidden beneath the forewings when the moth is resting
• Wing fringe: narrow pale or whitish edging may be visible along parts of the wing margins
• Larva: a densely hairy caterpillar with cream, yellowish, and black tufts; the head is reddish brown to orange-red, and the prolegs are reddish or pinkish
• Sex differences: males generally have more strongly feathered antennae; body pattern is otherwise similar between the sexes

Color can shift with the light. The thorax and abdomen may look nearly black in shade but flash vivid blue when direct light catches the scales. Worn adults can lose some wing fringe and may appear duller than fresh individuals.

Habitat and Behavior

Typical habitats include:

• moist meadows, grassy fields, and prairie openings
• roadsides, field margins, gardens, and open woodland edges
• wetland margins and other places with abundant grasses, sedges, and flowering plants
• sunny openings where adults can nectar and move among low vegetation

Behavioral notes:

• Activity: frequently active by day, though adults may also fly at night and come to lights
• Flight: usually flies low over grasses with a steady, fluttering movement that can suggest a small butterfly
• Perching: rests on grass blades, sedges, leaves, stems, and flowers, usually with the wings folded roof-like over the body
• Feeding: adults visit flowers for nectar
• Seasonality: in Minnesota, adults are most often encountered from mid-June into late July
• Larval association: caterpillars feed mainly on grasses but also use sedges and irises
• Overwintering: partly grown caterpillars overwinter in leaf litter or matted vegetation and resume feeding in spring

Adults are often easiest to notice when their orange heads or metallic blue bodies catch the light. A perched moth may conceal much of the blue abdomen beneath its wings, so a side view or a brief wing movement can reveal important field marks.

Identification

Key features for field diagnosis:

• Large wasp-moth build: broader-winged and more robust than the similar Yellow-collared Scape Moth
• Orange head and collar: the head is bright yellow-orange, and the collar narrows across the nape before widening toward the shoulders
• Metallic blue thorax and abdomen: blue iridescence is present on the thorax as well as the abdomen
• Broad dark forewings: uniform gray-brown to nearly black, without bold spots or bands
• Opaque black hindwings: visible in open-wing views and unlike the more translucent hindwings of the Yellow-collared Scape Moth
• Dark forewing costa: the leading edge remains dark rather than showing a conspicuous yellow basal section
• Comb-like antennae: especially broad and conspicuous in males
• Day-flying behavior: often active in sunny grasslands and flower-rich openings

For photographic identification, try to capture:

• a dorsal or three-quarter view showing the head, collar, thorax, and forewing shape
• a side view showing the metallic blue abdomen beneath the folded wings
• an open-wing view, when possible, showing the opaque dark hindwings
• a close view of the antennae and the shape of the orange collar
• habitat, date, and behavior, especially flower visits or low flight through grasses

Adult identification is usually reliable from a clear color photograph in Minnesota, but dark exposure can hide the metallic blue thorax. When the blue body or collar shape is not visible, compare the individual carefully with the Yellow-collared Scape Moth.

Similar Species

Use this section to distinguish Ctenucha virginica from likely lookalikes in Minnesota and the Upper Midwest.

• Yellow-collared Scape Moth (Cisseps fulvicollis): The most likely source of confusion. It is smaller and narrower-winged, with a more evenly transverse yellow-orange collar, a yellowish basal section along the forewing costa, little or no metallic blue on the thorax, and partly translucent hindwings. Virginia Ctenucha is larger and broader, with blue on the thorax and opaque black hindwings.

• Grapeleaf Skeletonizer (Harrisina americana): Smaller and more slender, with narrower wings and a less sharply defined orange collar. It is closely associated with grape and Virginia creeper. Virginia Ctenucha is heavier-bodied, broader-winged, and more extensively metallic blue.

• Virginia Creeper Clearwing (Albuna fraxini): A true clearwing moth with transparent areas in the wings and a more strongly wasp-shaped body. Virginia Ctenucha has fully scaled, opaque wings.

• Other tiger moths (Arctiinae): Some share warning colors or hairy larvae, but few adults in the region combine an orange head and collar, unmarked dark wings, and a metallic blue body.

• Dark butterflies: Daytime flight may initially suggest a butterfly, but Virginia Ctenucha lacks clubbed antennae and rests with the narrow dark wings folded over its body.

Larvae are more difficult to identify from photographs than adults. Their pale and black hair tufts, reddish head, reddish prolegs, host vegetation, date, and location should all be documented. Avoid handling unfamiliar hairy caterpillars, since their hairs can irritate sensitive skin even when the species is not considered medically significant.

Ecology and Notes

Virginia Ctenucha depends on open, grassy habitats through much of its life cycle. Caterpillars feed on several grasses as well as sedges and irises, while adults use nectar from flowers in the same meadows and field margins. This broad use of grasslike plants helps explain why the moth may occur in prairies, wet meadows, roadsides, and gardens rather than being tied to a single host species.

The adult’s orange-and-metallic-blue pattern resembles warning coloration found in wasps and other chemically defended insects. Its daytime activity makes that conspicuous pattern particularly visible to both observers and potential predators. Like other tiger moth relatives, Virginia Ctenucha can also produce ultrasonic signals associated with defense against bats.

Useful field notes:

• The metallic blue body may be hidden when the wings are tightly folded.
• Males can show remarkably broad, comb-like antennae in close photographs.
• Fresh adults have richer blue iridescence and cleaner pale edging on the wings.
• The moth often remains low in vegetation, where grass stems can obscure identification features.
• Adults may be seen by day at flowers and may also appear at artificial lights after dark.
• In Minnesota, the principal adult flight is concentrated in early to midsummer.
• Caterpillar records are most useful when they include the host plant or surrounding vegetation.

For field photography, follow an individual until it settles and then approach slowly from the side. A slightly elevated three-quarter view can show the orange collar, metallic thorax, wing shape, and antennae in one frame. If the moth briefly raises or opens its wings, an image of the abdomen and hindwings can make comparison with Cisseps fulvicollis much easier.

References

• BugGuide: Species Ctenucha virginica — Virginia Ctenucha https://bugguide.net/node/view/7773

• MinnesotaSeasons: Virginia ctenucha https://www.minnesotaseasons.com/Insects/Virginia_ctenucha.html

• Butterflies and Moths of North America https://www.butterfliesandmoths.org/species/Ctenucha-virginica

• NatureServe Explorer: Ctenucha virginica https://explorer.natureserve.org/Taxon/ELEMENT_GLOBAL.2.118734/Ctenucha_virginica

• Integrated Taxonomic Information System (ITIS): Ctenucha virginica https://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=188644

• iNaturalist taxon page https://www.inaturalist.org/taxa/119013-Ctenucha-virginica