Pegomya transgressa Zetterstedt 1846

2. Pegomya transgressa (Zetterstedt, 1846)

(Fig. 12)

Anthomyza transgressa Zetterstedt, 1846: 1770.

Pegomya transgressa (Zetterstedt); Hennig 1973c: 655, text figs 572, 573, table figs 781, 889, 927; Michelsen 1985: 59; Ackland 1989: 226, figs 31‒33, 39; Suwa 2013: 184.

Pegomya (Phoraea) transgressa (Zetterstedt); Griffiths 1983: 219, figs 301, 306‒310.

For further synonymy and references, see Hennig (1973c), Griffiths (1983) and Michelsen (1985).

Description. Very similar to P. fulgens, but smaller and differently coloured in both sexes. Size. Wing length up to 5.5mm. Male. Antenna wholly brownish black. Thorax wholly dark, covered in greyish or light brownish grey dusting. Calypteres whitish to pale ochre yellow, wing base of same colour. Legs brownish black except tibiae and extreme bases of mid and hind femora yellowish. Abdomen ochre yellow over ochre brown to extensively brownish black, covered in light grey dusting; narrow dark median stripe well visible on tergites II‒V or III‒V. Longest aristal pubescence only a little longer than greatest basal diameter of arista. Head normal sized, only slightly wider than high. Contiguous parafrontalia moderately narrow, throughout separating eyes by more than 0.5x width of anterior ocellus. Proepimerals: 1 seta and 1‒2 setulae. Lower calypter smaller than upper calypter and concealed behind it in lateral view. Terminalia indiscernible from those of P. fulgens except that the sternite V lobes as seen in broadest aspect (Fig. 12) appear less incised at inner margin. Female. Palp mainly brownish black, only diffusely yellowish basally. Postgenal setation all black. Thorax wholly dark, covered in light grey dusting with a brown tinge. Coxae and distal parts of femora more or less brownish infuscated. Proepimerals: 1 seta and 0‒1 setula. Oviscapt as in P. fulgens. Note. Griffiths (1983) and Ackland (1989), on my mistaken advice, noted that the oviscapt is more elongate in P. fulgens than in P. transgressa. This difference actually applies to females of the Pegomya fulgens and Pegomya furva species groups, respectively.

Material examined. [FMNH, MZLU, NHMO, ZMHU, ZMUB, ZMUC, ZMUT]. FINLAND: Lapponia inarensis, Lapponia enontekiensis. NORWAY: Oppland, Buskerud, Hordaland, Sør-Trøndelag, Nordland, Troms, Finnmark. RUSSIA: Murmansk. SWEDEN: Härjedalen, Jämtland, Norrbotten, Åsele Lappmark, Lycksele Lappmark, Lule Lappmark, Torne Lappmark.

Distribution. A species that replaces P. fulgens in the subarctic and low arctic zones of Fennoscandia. PALEARCTIC. Britain: Scotland (Ackland 1989); Norway; Sweden; Finland; Russia: Murmansk, Sakhalin (Suwa 2013). NEARCTIC. Widespread across northern North America (Griffiths 1983).

Biology. Ståhls et al. (1989) reared this northern species in large numbers from Leccinum (Boletaceae) in Finnish Lapland.