The relationship between wing venation and wing patterning in Micropterigidae

Multiple models have been proposed to explain the relationship between wing venation and wing patterning in forewings of Microlepidoptera. Lemche's model (1935, 1937) relates fascia (transverse stripes) to the points where veins fork within the wing, whereas Brown and Powell's model (1991; modified by Baixeras in 2002) relates fascia to the points where veins meet the costa of the wing. The most basal family of extant Lepidoptera, the Micropterigidae, contains a genus, Micropterix, in which many species have clearly defined fascia; wing pattern varies considerably between species in the genus, but wing venation does not. The relationship between venation and fascia in Micropterix rarely fits Lemche's predictions about the relationship between fascia and venation, but does conform to the Brown/Powell/Baixeras model. When the complete suite of primitive lepidopteran wing venation is taken into account, wing veins separate fascia from interfascial areas in all locations along the costa except for one; an additional vein, which would allow the model complete predictive power for fascia location, is present in certain Trichoptera. The inclusion of this last vein in the model has implications for wing-pattern and wing-vein homologies across all Lepidoptera.