A second update to the checklist of Finnish long-legged flies (Diptera: Dolichopodidae), with a re-evaluation of the status of Hydrophorus callosoma Frey, 1915

Abstract Eighteen species of long-legged flies (Dolichopodidae) are reported as new to Finland. A further species, Microphorella praecox (Loew), is confirmed as a Finnish species. The status of Hydrophorus callosoma Frey, 1915 is re-evaluated and a lectotype is designated for the species. Hydrophorus albosignatus Ringdahl, 1919 is found to be a junior synonym of Hydrophorus callosoma (syn. n.). Characters for identifying both sexes of Hydrophorus callosoma and Hydrophorus altivagus Aldrich are presented and illustrated with high-quality photographs.

This paper summarizes the changes that have occurred since the last update. A grand total of 18 species are added to the list of Finnish Dolichopodidae, bringing the total up to 264 species. The dolichopodid fauna of Finland is relatively well known, but at least 10-20 additional species can still be expected to occur in the country.

Diagnosis
Hydrophorus callosoma is externally most like H. altivagus Aldrich, 1911(=H. wahlgreni Frey, 1915. Both sexes can be identified by the armature on fore femora: there is only a single short row of 6-13 small ventral spines in the basal third of the fore femur. Anteroventral spines missing or at most 1-3 very short ones present (usually completely absent in females). H. altivagus has a row of strong anteroventral spines reaching the apical third of the femur in addition to the ventral spines. Other differences between the two species are tabulated in Table 1

Distribution
Sweden, Finland and North-Western Russia (Murmansk and Archangelsk Oblasts).

Taxon discussion
Richard Frey described Hydrophorus callosoma as a variety of on the basis of two female specimens. He did, however, express doubt about it's true status. The name has later been synonymed with H. wahlberg Frey, 1915(Negrobov 1977, which in turn was synonymised with H. altivagus Aldrich, 1911 (Hurley 1985 The Kantalaks specimen is here designated as the lectotype of H. callosoma Frey, 1915. This choice is made because only this specimen does actually match Frey's original description "...near the previous species [=H. wahlbergi], from which is differs by its much more brilliant coloration and the pale hairs on the sides of the abdomen" (Frey 1915). The Kem specimen-like all specimens of both species-have pale hairs on the ventral margin of the tergites only. Because of the distortion of the abdomen of this dry-pinned female, the ventral hairs are visible when viewed from above.
H. callosoma Frey, 1915 is thus a senior synonym of H. albosignatus Ringdahl, 1919 and becomes the valid name for this species (syn. nov.).

Taxon discussion
Medetera belgica was based on a single female Parent 1936. Negrobov andStackelberg 1972 redescribed the species based on male specimens from the Kola Peninsula in Russia, some 2,500 km away, without studying the holotype of M. belgica. It is certainly possible that the Finnish specimens identified as M. belgica sensu Negrobov are not conspecific with Parent's original types. M. belgica was synonymised with M. muralis by , but this synonymy has been disputed (Pollet 2013). In Finnish material the leg colour characters and differences in male genitalia between the two species (M. muralis and M. belgica sensu Negrobov) are well defined and constant.

Distribution
New to Finland. Previously known from Estonia and Russia (Negrobov 1991, Grichanov 2002b

Distribution
New to Finland. A rare species previously known from Sweden and Alaska (Ringdahl 1920, Pollet 2013.

Distribution
New to Finland. Widespread in Europe, but many records should be confirmed due to the frequent misuse of this name for Dolichopus trivialis Haliday, 1832 (Pollet 2013).

Taxon discussion
This name has a confused history of use, which can be traced back to von Stackelberg (1930)

Distribution
New to (present-day) Finland. Previously recorded as Finnish based on specimens from areas ceded to Russia after the second world war (Kahanpää and Grichanov 2004). Also reported from Sweden, northern Russia, Mongolia and (doubtfully) in the Oriental region (Frey 1915, Pollet 2013.

Biology
A species of eutrophic calcareous spring-fed fens in northern Finland.

Distribution
New to Finland. An east European species, previously recorded from Austria, Hungary, European Russia and Ukraine (Pollet 2013).

Biology
Caught on the silt banks of a small stream in a herb-rich forest.  (Negrobov 1991, Ringdahl 1949).

Biology
C. femoratus is common and occasionally abundant along forest streams in the central boreal zone of Finland. Its rarity in museum collections is explained by the combination of a northern distribution, an early/late occurrence of the adults and a species-poor habitat often skipped by collectors of Dolichopodidae: the adults are on the wing in May and September when these forests may still have a partial snow cover.

Distribution
New to Finland. Previously found in the United Kingdom, Germany, Switzerland, France, the Czech Republic and Slovakia (Drake 2008, Pollet 2009, Pollet 2013.

Biology
Locally common on open seashore or lakeshore wetlands characterised by Potentilla palustris intermixed with large Carex species. Unlike Achalcus flavicollis (Meigen, 1824) and Achalcus vaillanti Brunhes, 1987, A. nigropunctatus is only rarely caught in pure Phragmites stands.