Stigmella poterii
Diagnosis. Similar to S. filipendulae and S. ulmariae; poterii differs only in its normally more oblique, distinct and more postmedial fascia. The male genitalia of poterii, S. filipendulae and S. ulmariae all have a large apical cornutus and fine proximal spines in aedeagus; poterii differs from the two other species in having broader uncus, less pointed valvae and larger aedeagus with more numerous small spines. The female genitalia of poterii, S. dryadella, S. filipendulae and S. ulmariae are probably not reliably separable. The illustrations of the female genitalia of these four species demonstrate their combined variation.
Male. Wingspan: 3.5-5.0 mm. Head: frontal tuft pale ochreous to dark brown (in S. Scandinavia usually ochreous brown); collar dark brown; scape pale yellow; antenna three-fifths length of forewing. Thorax dark brown. Forewing: area proximal to fascia dark brown with bronzy lustre to dark purplish brown; fascia distinctly postmedial, of varying width, slightly inwardly oblique, shining golden; distal to fascia slightly darker than proximal part, sometimes with few dark blue scales; terminal cilia grey. Hindwing and cilia grey. Abdomen dark grey to black. Female. Wingspan: 3.5-5.0 mm. Male genitalia. Vinculum distinctly emarginate. Uncus large, subtriangular, with deep narrow medial fissure; paramedial notches indistinct or absent. Valva with rounded inner lobe with distinct protuberances; distal process relatively long and blunt. Transtilla with distinct short and pointed sublateral processes. Juxta absent. Aedeagus as long as genital capsule; with a large cornutus with broad base near tip, proximal part with long 'tail' of numerous (approx. 100) needle-like cornuti. Female genitalia. Corpus bursae small, without pectinations. Vestibulum moderate, bilobed. Accessory sac about as large as corpus bursae. Ductus spermathecae without spines. Apophyses short. Ovipositor not protruding.
Host plants: Potentilla erecta, P. palustre and possibly other Potentilla spp., Rubus chamaemorus, R. saxatilis and R. arcticus, Sanguisorba officinalis and S. minor. Egg: laid on a vein, usually on upper surface of leaf. Larva: dark yellow. Mine : short, about 3 cm long, first half narrow, following a vein or the leaf margin, second half abruptly or gradually widening, contorted and frequently forming a blotch; frass throughout mine in a central line. Normally only a single mine per leaf. Cocoon: brown.
Widespread in Denmark, Sweden, Norway and Finland. - In Ireland and Great Britain, through central Europe to Hungary.
Voltinism: in C. Europe, Denmark and S. Sweden two generations per year. In the rest of Scandinavia only one, mines from the middle of August to early September. In damp woods, wet meadows and bogs, but also in limestone grassland.
Description based on Johansson and Nielsen (1990)
