Identification
Adult Markings: Hodges (1986) reported that D. inserrata and D. fistuca have nearly identical external coloration and patterning and require the examination of genitalia for accurate identification. Both species have a two-toned forewing with a creamy-yellow to orangish-yellow region that fills most of the subcostal portion of the wing, along with two large, brownish-black to blackish marks on the remainder of the wing. The first extends from near the wing base along the inner margin and gradually widens near the middle of the wing, then curves inward and terminates on the inner margin at around three-fourths the wing length. The second is a semi-oval mark that fills most of the apical third of the wing. The two marks meet at around three-fourths the wing length and are partially separated by a broadly-angled tooth that tapers to a blunt tip just beyond the middle of the wing. Both species have a noticeable indention along the edge of the basal mark at around two-fifths the wing length that helps to separate these from D. flavocostella . D. inserrata , the posterior margin is generally straight from the wing base to two-fifths the wing length where the black band bulges outward. It is also either straight or slightly convex as it cuts diagonally across the wing from about two-thirds the wing length to the subapical region of the costa. In contrast, the basal and terminal sections are usually bowed inward for D. fistuca . When combined with the middle section, these produce a pattern of three concave arches. D. fistuca that have been identified based on genitalia tend to have a dull orangish-yellow color in the subcostal region. In contrast, D. inserrata from the mountains that have been identified based on genitalia tend to have a cream-colored to dull white subcostal region. Dichromeris fistuca from the Coastal Plain also commonly has one or more small teeth or indentions between the wing base and the major indentation at two-fifths, while D. inserrata from the Blue Ridge does not. In general, these two groups fit the patterns in maculation described above by Hodges (1986). D. inserrata from the mountains (see examples on iNaturalist), but have not been identified based on genitalia to confirm that they are this species. We elected to treat these as D. inserrata based on their maculation and geographic distribution, with the caveat that species from this region need confirmation based on the examination of genitalia. Hodges (1986) reported the range of D. fistuca to include Florida northward to coastal South Carolina, which is consistent with our tentative assignment of Piedmont populations to D. inserrata , i.e., that D. fistuca is rarely found outside of the Coastal Plain.
Forewing Length: 5.4-6.5 mm (Hodges, 1986).
Adult Structural Features: Hodges (1986) has illustrations and descriptions of the male and female genitalia. Also, see images from North Carolina specimens below.
Genitalia and other structural photos
Adult ID Requirements: Identifiable only by close inspection of structural features or by DNA analysis.
Immatures and Development: As of 2025, we are not aware of any documentation of the host plants or larval life history.
Larvae ID Requirements: Identifiable only through rearing to adulthood.
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