Scatella (Scatella) lacustris

Scatella (Scatella) lacustris (Meigen, 1830), revised status

(Fig. 8)

Ephydra lacustris Meigen, 1830: 118.

Scatella lacustris: Becker, 1902: 310 (combination), synonymy with S. stagnalis (Fallén, 1813). Scatella tenuicosta Collin, 1930: 136, new synonym.

Scatella thermarum Collin, 1930: 138, synonymized with S. tenuicosta Collin, 1930 by Olafsson, 1991: 31.

Type material examined: one female lectotype of the senior synonym, herein designated, double mounted on a thin pin in a paper square, in good condition, but covered with some dust, right wing folded, labelled: “26.98 40" (rounded label), on the reverse “Meigen” (handwritten), “ lacustris ” (handwritten) preserved in MNHM; the male lectotype of the junior synonym, herein designated, in good condition labelled: "Pitsea 7/6/94 ", " Scatella tenuicosta Collin " - 1 ♂; paralectotypes: two females with the same labels (one with posterior margin of the right wing slightly torn); a male in good condition labelled: "Pitsea 7/6/94 ", " Scatella tenuicosta Collin Det. I. Lansbury 197"; a male with removed abdomen, labelled: "Walton-on-Naze 9. 6. 0 8 Col. Y.", its terminalia in Canada balsam on a celluloid square bearing a label: "Walton-on-NAZE 9. VI. 1908 Col. Yerbury", " Scatella tenuicosta Collin ", all preserved in OUMNH. According to Mathis and Zatwarnicki (1995) some type material is also present in NHMUK and MZLU.

Other material examined: Numerous specimens from Austria, Belgium, Bulgaria, Czechia, Denmark, Finland, France, Germany, Great Britain, Greenland, Hungary, Iceland, Ireland, Italy, Netherlands, Norway, Poland, Portugal, Romania, Russia, Spain, Sweden, Switzerland, United Kingdom, United States (Arizona, Illinois).

The type locality of senior synonym was not given, and the specimen was possibly collected in Central Europe (France or Germany). Type locality of the junior synonym: Essex: Pitsea and Walton-on-Naze; Dorset: Arne; Glamorgan: Porthcawl; Norfolk: Palling-on-sea; Suffolk: Aldeburgh, Felixstowe, Butley, Newmarket (Great Britain).

Diagnosis. The species is closely related to S. stagnalis (Fallén), but is distinguished from other species by the wing with spot 3 (distal spot in R5) narrowest in middle; costal section II longer than III (Fig. 8); female sternite 7 a single sclerite. Male terminalia illustrated by Olafsson (1991; figs 15d–h, page 30) and Beshovski (2009, fig. 147, pages 370–371).

Distribution. Afrotropical: Cape Verde Islands. Nearctic: Greenland, United States (Arizona, Illinois, Oregon). Palaearctic: Austria, Azores, Belgium, Bulgaria, Canary Islands, China, Cyprus, Czechia, Denmark, Egypt, Finland, France, Germany, Great Britain, Greece, Hungary, Iceland, Ireland, Italy, Jordan, Madeira Islands, Norway, Poland, Russia (European Territory), Serbia, Slovakia, Spain, Sweden, Switzerland, Tunisia, Turkey.

Remarks. Characters of the lectotype: wing spot 3 narrowest in middle; costal section II longer than III; female sternite 7 a single sclerite, characterize S. tenuicosta and distinguish it from S. stagnalis (Fallén). Becker (1902) had not realised there was a second species and incorrectly placed lacustris in synonymy with stagnalis.