Field Guide Descriptions: Leckie and Beadle (2018). | Online Resources: MPG, BugGuide, iNaturalist, Google, BAMONA, GBIF, BOLD | Technical Description, Adults: Duckworth (1964), Murtfeldt (1890). | Technical Description, Immature Stages: Murtfeldt (1890), Eiseman (2019). | |
Adult Markings: Adults are readily identified by the conspicuous whitish triangular mark that occurs about midway on the costa of each forewing. A small white dot occurs near the tip of each triangular mark. The fringe on the outer margin is whitish, and the legs are predominantly white and contrast with the shiny black ground color. M. tortriciformella is somewhat similar, but lacks the triangular marks on the forewings. |
Wingspan: 10-12 mm (Duckworth, 1964) |
Adult Structural Features: The genitalia are described and illustrated by Duckworth (1964). |
Adult ID Requirements: Identifiable from good quality photos of unworn specimens. |
Immatures and Development: The only detailed description of larval development is by Murtfeldt (1890) in Missouri, where larvae first appeared on Post Oak (Quercus stellata) in late summer and required about a month to mature. Hatchlings begin as leafminers, then switch early in development to feeding externally on the undersurfaces of the leaves. The older larvae skeletonize leaf surfaces beneath protective webs that are densely woven, thickest near the middle, and attenuated near the ends. Frass is ejected from the web. Just prior to pupating, late-instar larvae thicken the densest parts of their feeding webs. Each larva then cuts out a broad oval section around the densest part of the web that is about 13 mm long. The cut edges are bound together and the entire structure in dragged away from the injured part of the leaf and suspended from the underside of the leaf by a broad band of silk. The larvae pupate within these structures and overwinter until the following year when the adults emerge. Full-grown larvae are about 8 mm long, and are dingy, translucent white with a small head that is about one-half the diameter of the first thoracic segment. See Eiseman (2019) and Marquis et al. (2019) for images of the larvae and webbing. |
Larvae ID Requirements: Identifiable from good quality photos, especially where associated with known host plants. |