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Field Guide Descriptions: | Online Photographs: MPG, BugGuide, iNaturalist, Google, BAMONA, GBIF, BOLD | Technical Description, Adults: Forbes (1923) | Technical Description, Immature Stages: Eiseman (2019) | |
| Adult Markings: The following is based in part on the description in Forbes (1923). The head is dark yellowish. The labial palp is dull white to dull yellowish with the third segment dark on the outer side. The antenna is light brown with faint darker annulations and extends to the tip of the wings. The forewing ground color varies from reddish brown to purplish brown. A conspicuous, truncated triangular patch is present at about two-fifths. It extends from the costa and terminates at the fold before reaching the dorsal margin. The triangular patch has a series of 4-7 small dark spots along the costal margin and is asymmetric, with the apical end having a more exaggerated taper. The fringe is yellowish and tipped with black. The tibia and femur of the front and middle leg are dark and concolorous with the ground of the forewing, while the tarsi are white with fine dark markings near the tarsal joints. The rear leg is dull whitish, with faint dark marking near the tarsal joints. |
| Wingspan: 10 mm (Forbes, 1923). |
| Adult ID Requirements: Identifiable from good quality photos of unworn specimens. |
| Immatures and Development: The larvae produce linear blotch mines on the undersides of birch leaves. The eggs are often laid near a side vein and the linear portion may run a short distance along the vein before crossing to an adjoining vein. The linear portion runs for only 1-2 cm before expanding into a small, elongated blotch. The later instars leave the blotch and feed within a conical roll that begins at the leaf apex, or they may simple fold the leaf edge to make a shelter. The final instar exits the roll to spins a whitish cocoon in a leaf fold (Eiseman, 2019). |
| Larvae ID Requirements: Identifiable from good quality photos, especially where associated with known host plants. |