Taxonomic Notes on the Genera Pl Atycheirus and Melanostoma (Dipt., Syrphidae) with Lectotype Designations by HUGO ANDERSSON

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Taxonomic Notes on the Genera Pl atycheirus and

Melanostoma (Dipt., Syrphidae)

With Lectotype Designations

By HUGO ANDERSSON Zoological Institute, 223 62 Lund, Sweden

Abstract Characters separating the genera Platycheirus M. mellinum L. Lectotypes are designated for and Melanostoma are discussed. The name Melano- Scaeva ambigua Fall., S. transfuga Zett., and S. stoma Schin. is restricted to species with a distinct dubia Zett. The two firstmentioned belong to type of metasternum present in the type species, Platycheirus and the latter to Melanostoma s. str.

The delimitation of the genus Melanostoma treats it as a distinct genus, while S6guy Schiner (I96I) and Stone et al. (1965) list it as a Problems have arisen about the proper de- synonym of Melanostoma. limitation of the genus Melanostoma Schiner, Fluke (1957) has published a study on the 1860. As far as the European fauna is con- male genitalia of Melanostomini. He found cerned it has been difficult to find good that the species of Platycheirus are distinctly characters to separate Melanostoma from Mel- different from those of Melanostoma in the angyna Verrall, Epistrophe Walker, Platychei- build of the male genitalia. By the presence of rus Lep. et. Serv., etc. Kanervo (1938) has a thumb-like processus the styles (paralobi, discussed the matter and reviewed earlier forceps) of Platycheirus are basally bifid and works on it. in this genus the superior lobes are recurved From Northern Europe five Melanostoma- and sickle-shaped. The styles of Melanostoma species have been listed: mellinum L., scalare are simple and the superior lobes are squarish Fabr., dubium Zett., ambiguum Fall., and and not recurved. Cf. fig. 2 and 3. trans f ugum Zett. It has been questioned There is also another distinct character dis- whether the latter two really belong to Mel- criminating Platycheirus and Melanostoma, anostoma, as they have some characters typi- which I have not found to be mentioned in cally found in Platycheirus: specialized hairs the literature. In the type species of Melano- and bristles on male legs, and distinct square stoma, Musca mellina L., the strongly sclerotiz- yellow markings or blue dustspots on abdomen. ed part of metasternum is largely reduced and Enderlein (1938) described the new genus shows a spearhead-shaped figure (fig. i A). Pachysphyria with ambiguum as typus generis. In Platycheirus this part of metasternum is He also listed dubia Zett. in this genus which fully developed (fig. i B). I think this is an he discriminated from Melanostoma on rather important character and that the reduced indistinct characters: first segment of hind metasternum is characteristic for all true Mel- tarsi in male sex more or less strongly dilated anostoma species. Melanostoma scalare Fabr. (in Melanostoma not dilated), hind margin of and M. dubium Zett. (vide below) agree with eyes in male and female quite stright (in M. mellinum L. in the general type of male Melanostoma a little incurved). Szilády genitalia and in the build of metasternum. (1940), Frey (1946), Coe (1953), Stackelberg Males identified as Scaeva ambigua Fall. (1958), and Bafikowska ( i g63) do not men- and S. transversa Zett. have male genitalia of tion the genus Pachysphyria. Goffe (lgS2) Platycheirus type with branched styles and 237

Fig. i. Metasternum and hind coxae of Al Melanostoma mellinum L. and B) Platycheirus albimanus Fabr. Fig. 2. Ventro-lateral view of epandrium with styles and cerci of A) Platycheirus albimanus Fabr., B) Platycheirus ambiguus Fall., and C) Melanostoma mellinum L. Fig. 3. Superior lobes of A) Platycheirus albimanus Fabr., B) Platycheirus ambiguus Fall., and C) Melanostoma mellinum L.

sickle-shaped superior lobes. The metasterna species should be transferred to Platycheirus are fully developed. They also possess other and that Pachysphyria End. is a synonym of characters commonly found in Platycheirus, Platycheirus Lep. et Serv. It is possible that such as specialized hairs and bristles on legs, Pachysphyria should be retained as a subgenus inflated frons and bluish dust on abdominal of Platycheirus in agreement with the opinion spots. Therefore, I consider that these twc of Dusek and L6ska (1967).