These very pretty little moths in the family Erebidae are common, but, at least in my experience, seldom abundant. By which I mean that I get one of these visiting my lights most times that I set up, but I don’t remember ever seeing more than 2 in a night. And because they are eminently identifiable I often forget to take photos, so that every time I think about doing a profile of Idia americalis (American Idia moth) I realize that I don’t have enough pics. But I have finally remedied that, although I do not have any ‘money shots’ for scale, because I’ve never needed to take one home to identify it.
They belong to the subfamily Herminiinae, which are commonly called the litter moths because their larvae are forest floor detritivores, although Idia americalis also feeds on lichens and fungi, and may also do cleanup duty in ant nests. The same colors that make them so attractive on a sheet or other solid backdrop are probably very good camouflage when ovipositing amongst leaf litter and some lichens, though not so effective when they are perched on moss.
Description– “A small (2-3 cm. wingspan), broad-winged and rather delicate moth. The forewings are light blue-grey and brown, marked with fine black jagged cross lines. The lines thicken where they meet the costa, forming a series of three prominent black spots. The reniform spot is usually filled with yellowish or orange scales. Three parallel lines partially cross the hindwings. Specimens from cooler and more mesic environments in the mountains and northern areas may be dusky and have the makings “blurred”. Specimens from the more xeric areas of the southern boreal forest south tend to be larger, paler, and more crisply marked. Both sexes are similar. They may be mistaken for a small geometrid moth.” Idia americalis – University of Alberta Museums Search Site
Similar species– Other Idia sp. in our region lack dark spots where the transverse lines meet the costa.
Habitat– “This species is common and widely distributed in moist forests throughout much of North America. In the Pacific Northwest, it is common in coastal rainforests, mixed hardwood forests at low elevations west of the Cascades, and in mixed hardwood-conifer forests at higher elevations in both the Cascades and Rocky Mountains.” PNW Moths | Idia americalis
Range– “This species is widely distributed in North America. It is common and widespread in the East…Idia americalis is found in forests throughout the Pacific Northwest. It is most common in western Oregon and Washington.” PNW Moths | Idia americalis
Eats– “larvae feed on lichens (2); dead leaves (Jim Sogaard); fungi (MJ Hatfield); may be a detritivore in ant nests (Pacific Northwest Moths)” Species Idia americalis – American Idia – Hodges#8322 – BugGuide.Net; since the adults come to bait they must eat either nectar or decomposing fruit, and possibly both.
Eaten by– Presumably a host for parasitoids in Hymenoptera and Diptera, and probably preyed upon by insectivores of all classes, but I can find nothing specific for this species.
Life cycle– Overwinter as larvae; may be multivoltine in good conditions in relatively warm climates.
Etymology of names– Idia “Appears to be a variant of Greek idio “one’s own, peculiar” (1). The Century Dictionary (2) gives this (Greek ιδιος) as the origin of the (obsolete) name for a fly genus Idia Meigen, 1826.” Genus Idia – BugGuide.Net. The specific epithet americalis refers to this being an American species.