Pyrophaena rosarum (Fabricius, 1787):341

Pyrophaena species are similar to Platycheirus (some authors consider Pyrophaena as a subgenus of Platycheirus) but differ by having the wing shorter than abdomen; abdomen broad, or mostly red, or black with 2 pale maculae on tergum 3.

Pyrophaena rosarum (Fabricius, 1787).

Fabricius, J.C. (1787) Mantissa insectorum: sistens eorum species nuper detectas, adiectis characteribus genericis, differentiis specificis, emendationibus, observationibus. Vol. 2, [2] + 382 pp. C.G. Proft, Hafniae [=Copenhagen]. [1787.12.27]

Adapted from Vockeroth (1992).

MALE.

Similar to male of Pyrophaena granditarsis, differing as follows:

Head: face slightly receding, with smaller tubercle. Antenna usually with basoflagellomere orange to orange-brown below.

Thorax: Wing in some specimens with faint postmedian cloud on anterior half. Pro- and mesofemora yellow on about apical half; pro- and mesotibiae and tarsi yellow; metatibia with basal one-third and in some specimens narrow apex yellow; metatarsus yellow with dorsal surface of first tarsomere and of last one or two tarsomeres in some specimens dark brown. Legs slender, without distinctive hairs or bristles. First tarsomere of metaleg about six times as long as greatest depth.

Abdomen mostly black. Terga 3 and 4 each with pair of yellow posteriorly rounded lateral maculae on anterior margin. Sterna black; sterna 3 and 4 each with broad anterior yellow fascia. Surstylus without distinct dorsobasallobe. Paramere with slender base and well-separated long slender spine. Aedeagus with strong subbasal dorsal lobe.

FEMALE.

Frons shining except for two very small silvery pollinose lateral maculae at two-thirds length. Wing cloud often more distinct and slightly larger. Tarsi distinctly wider than in male. Markings of terga less clearly defined than in male and yellow-orange rather than yellow; tergum 2 black or with pair of rounded yellow maculae confluent medially in some specimens; tergum 3 commonly with maculae confluent and in some specimens covering most of tergum.

Pyrophaena was described by Schiner (1860) for Syrphus rosarum Fabricius, 1787. Vockeroth (1990) considered it a synonym of Platycheirus, and some authors (Thompson 2010) gave to Pyrophaena the status of a subgenus.

Mengual et al. (2008) using molecular characters recovered Pyrophaena granditarsis as a different genus from Platycheirus and considered Pyrophaena a valid genus.

Synonyms:

Musca rosarum Gmelin, 1790: 2877.

Syrphus rosarum Fabricius, 1787: 341.

Pyrophaena rosarum var. duplicata Fluke, 1922: 228.

Body lenght: 7.4-9.1 mm (Vockeroth 1992).

Genus Pyrophaena, like Syrphocheilosia, Pseudoplatychirus, Spazigaster and Rohdendorfia, were treated as subgenera of Platycheirus by some authors (Hull 1949a; Vockeroth and Thompson 1987; Thompson and Vockeroth 1989; Thompson and Rotheray 1998) and others treated it as a separate genus (Williston 1887; Shannon 1921, 1922, 1923; Goffe 1952; Wirth et al. 1965; Dusek and Laska 1967; Shatalkin 1975; Rotheray and Gilbert 1989, 1999). Molecular evidence by Mengual et al. (2008) placed Pyrophaena close to the other traditional subgenera of Platycheirus except Pseudoplatychirus, a hypothesis supported also by larval characters (Rotheray and Gilbert 1999). Shatalkin (1975) also mentioned some differences in the lobes of the surstyli comparing Pyrophaena with Platycheirus.

Adults visit flowers of Caltha, Knautia, Lythrum, Potentilla erecta, Ranunculus (Speight 2010).

The flight period for European specimens is from May to September (Speight 2010).

Holarctic species found from Fennoscandia south to Iberia and the Mediterranean; from Ireland eastwards through most of Europe (extremely localised in the Alps) into European parts of Russia; in Siberia from the Urals to the Altai. In North America from Alaska to Nova Scotia and south to Wisconsin and New Jersey (Speight 2010).

Adults of P. rosarum flies among tall waterside and fen vegetation; males hover within 2 m of the ground in sparsely vegetated patches (Speight 2010).

Preferred environment: wetland/freshwater; pond, stream and river margins with tall herb vegetation and fen, around the periphery of raised bogs, Salix swamp, also humid, seasonally-flooded, unimproved grassland (Speight 2010).