About Stigmella hemargyrella (Kollar, 1832) Gerasimov, 1952
Stigmella hemargyrella is a moth species in the family Nepticulidae. It is distributed across most of Europe, and is absent from Iceland, Norway, Finland, Portugal, and most of the Baltic region. This species has a wingspan of 5 to 6 mm. Its head is light ochreous-yellowish, and its antennal eyecaps are whitish. The forewings are deep shining bronzy, with a golden-tinged silvery-metallic, barely oblique fascia located at the two-thirds position of the wing. The apical area beyond this fascia is dark purple-fuscous. The cilia surrounding the wing apex are white, beyond a blackish median line. The hindwings are a rather dark grey. Adult moths of this species are bivoltine, flying in two generations: the first from April to May, and the second from July to August. Adults can often be found resting on tree trunks. Females lay eggs on either side of host leaves. Pale yellowish-white larvae develop inside leaf mines, feeding on Fagus sylvatica and Fagus sylvatica orientalis. The mine created by this species is a sinuous gallery. In its early stage, the mine is relatively narrow, with a central line of dark frass. As the larva grows, the mine widens. In the middle portion of the mine, frass is arranged in a series of arcs or coils. Unlike the mines of Stigmella tityrella, which rarely cross leaf veins, the mine of Stigmella hemargyrella can cross veins. In the final stages of the mine, frass is more irregular and concentrated in the center of the gallery.
