American idia moth

American idia moth is a common, medium-sized, litter moth. It occurs in the United States and southern Canada east of the Great Plains, west of the Rocky Mountains, and in central Colorado and New Mexico. It is common in the wooded regions of Minnesota. Caterpillars feed on lichens, dead leaves, and fungi, and possibly also on the detritus in ant nests. Adults are found from late May to early October in moist woodlands. They often feed on lichens on the trunks of trees.

Adults are roughly triangular in shape (deltoid), are ½″ to 9⁄16″ (13 to 14 mm) in length, and have a ¾″ to 13⁄16″ (20 to 30 mm) wingspan. Moth size is often given in terms of forewing length, which in this case is ⅜″ to 9⁄16″ (9 to 14 mm)

The forewings are broadly rounded on the outer margin. They are gray or light brown in the basal half, becoming darker and tinged with brown, brownish-orange, brownish-red, or brownish-yellow on the outer half, and they are crossed with several pale jagged lines. From the wing base to the tip there is a basal line, an antemedial (AM) line, a median line, a postmedial (PM) line, a subterminal (ST) line, and a terminal line. The AM line is pale and is bordered below with dark brown. The median line is dark brown. The PM and ST lines are pale and are bordered inside with dark brown. There is a dark brown bar on the leading edge (costal margin) at the ends of the AM, PM, and ST lines. This feature readily distinguishes American idia moth from all other idia moths. The terminal line is dark brown and thin on the inner half, becoming a broader patch on the outer half. The fringe is checkered. The round spot (orbicular spot) in upper median area is small and is colored the same as the tinge on the rear half of the wing. The kidney-shaped spot (reniform spot) in the rear half of the median area is the tinge color but darker and with a pale border.

The hindwing is light gray with several dark and light lines.

The head and thorax are the same color as the forewings. The antennae on both sexes are slender and thread-like. On the male they are moderately covered with long bristles on both sides (biciliate).

The caterpillar is less than ¾″ (2 cm) long. The body is dark smoky brown and has several rows of orangish, bristle-like hairs (setae). The setae are pale at the tip. The caterpillars of most idia moths can be identified only by rearing them into adults.

Total length: ½″ to 9⁄16″ (13 to 14 mm)

Wingspan: ¾″ to 13⁄16″ (20 to 30 mm)

Forewing length: ⅜″ to 9⁄16″ (9 to 14 mm)

Moist forests and woodlands

Two or more generations per year: May to October

Adults are active at night and will come to lights.

Lichens, dead leaves, fungi, and possibly detritus in ant nests

Lichens

Sources

4, 21, 24, 27, 29, 30, 71, 75, 82, 83.

Common

In 2011 the family Arctiidae (tiger moths and lichen moths) was transferred to the family Erebidae mostly intact but demoted to a subfamily. The former subfamilies are now tribes, the former tribes now subtribes.

Found this moth on my sliding glass door today. I had just watered my geraniums, so maybe came from them.

Idia americalis (American idia moth)

American Idia (Erebidae: Idia americalis) Dorsal View
Carl Barrentine

American Idia Moth resting for the night
Insects and Animals

Luciearl
3/13/2024

Location: Lake Shore

Location: Albany, NY

Location: Barnes Prairie house next to, Racine Co., WI