Sphecomyia brevicornis Osten Sacken, 1877

M. Moran, Kevin & H. Skevington, Jeffrey, 2019, Revision of world Sphecomyia Latreille (Diptera, Syrphidae), ZooKeys 836, pp. 15-79 : 25-26

Sphecomyia brevicornis Osten Sacken, 1877 Figs 2B, 5B, 16A, 17A, 18A, 21G, H, 22A, 23

Sphecomyia brevicornis Osten Sacken 1877: 341 - Röder 1879: 97; Williston 1882b: 328, 1886: 258; Aldrich 1905: 404; Osburn 1907: 4, 1908: 11; Kertész 1910: 348; Cole and Lovett 1921: 293; Shannon 1925: 43; Hull 1949: 264; Stone et al. 1965: 612; Weisman 1965: 266, 1966a: 51, 1966b:193; Boyes and van Brink 1967: 432, 1970: 212; Cole and Schlinger 1969: 331; Telford 1975: 21. Type locality: Webber Lake, Sierra County, California. [MCZ]

Sphecomyia vespiformis of Curran 1932: 8, not Gorski 1852. Misidentification.

Diagnosis.

Species most similar to S. interrupta sp. n. and S. sexfasciata sp. n. but can be distinguished by the following characters: scutum with two pairs of pruinose vittae; cell c completely microtrichose; antenna possessing a 2:2:1 ratio of segments; frons bare; anepimeron not pruinose; anterior three-fourths of scutellum pruinose; medial facial vitta not interrupted by a spot of pruinosity.

Redescription.

Male. Body length: 11.0-16.0 mm. Wing length: 9.7-10.9 mm. Head. Face yellow pruinose with shiny, black, medial vitta extending from oral margin to base of antenna; frons broad, about as long as broad at antenna, two-thirds as broad at vertex as at antenna, bare, with yellow pruinosity along posterior third; vertex triangular, longer than broad, shiny, with ocellar triangle black pilose; postocular border yellow pruinose; postocular pile black; occipital pile yellow; male narrowly dichoptic; antenna black, black pilose, with length of segments roughly in a 2:2:1 ratio.

Thorax. Matte black; postpronotum yellow pilose; scutum yellow pilose, except with black pile posteromedially; scutellum yellow pilose anteriorly and black pilose posteriorly; postalar callus, proepimeron, posterior anepisternum yellow pilose; posterior katepisternum yellow pilose with broadly separated patches; anterior anepimeron yellow pilose; metasternum yellow pilose; postpronotum, anterior three-fourths of scutellum, broad posterior margin of anepisternum and dorso-posterior corner of katepisternum yellow pruinose; anepimeron usually shiny, rarely with weak pruinosity; scutum with two pairs of pruinose vittae: anterior pair long, running from anterior edge of scutum to transverse suture; posterior pair shorter and terminating before posterior edge; ventral calypter with long yellow pile.

Legs. Foreleg reddish-yellow, except basal four-fifths of femur and last three tarsomeres black; midleg reddish-yellow, except basal four-fifths of femur and last three tarsomeres black; hind leg reddish-yellow, except last two tarsomeres black; legs yellow pilose, except black pilose on last three tarsomeres; hind coxa yellow pruinose.

Wing. Hyaline; microtrichia absent from following areas: broad anterior margin of cell cua.

Abdomen. Tergites and sternites shiny to sub-shiny, black with yellow pruinose markings as follows: tergite 1 pruinose along posterior margin; tergite 2 with broad, interrupted, truncate medial band which meets a broad, uninterrupted posterior band in the posterolateral corners of tergite; tergite 3 with broad medial band, sometimes very narrowly interrupted, that joins with broad posterior band in two places, creating a medial diamond-shaped spot of no pruinosity; pattern on tergite 4 same as tergite 3; sternite 1 shiny; sternites 2 to 4 variable pruinose: ranging from almost completely pruinose, with a small region of non-pruinosity posteromedially to mostly pruinose, except with narrow anterior border and transverse subapical band shiny to dull black; sternites 6 to 8 pruinose; pile of abdomen yellow.

Male genitalia. Surstylus elongated, about two and a half times as long as broad, apex acute, directed ventrally; pile on dorsal surface of surstylus, increasing in length posteriorly; minute spines on ventral surface and apical three-fourths of lateral inner and outer surface; basal fourth of the ventral surface of the surstylus produced into a lobe directed ventrally, with minute pubescence on ventral and lateral inner surface; cerci rounded, with invagination on posterior border; aedeagus as in Fig. 2B.

Female.

Similar to male except normal sexual dimorphism.

Distribution.

U.S.A.: Washington, Oregon, California, Idaho, and Montana. Canada: Alberta and British Columbia (Fig. 23). Extends south from southern British Columbia, as well as the southeastern corner of Alberta, through the coastal and mountainous areas of Washington state, through Oregon and into the Sierra Nevada and midcoastal regions of California. Also known from forested regions of northern Idaho and western Montana.

Biology.

Collected visiting flowers of Vaccinium L. sp., Phacelia Juss. sp., Ceanothus L. sp. and Berberis aquifolium Pursh. Recorded flying late April through late July, with one outlier in late August.

Remarks.

Sphecomyia brevicornis shows intraspecific variation on sternites 2 to 4. Northern specimens (i.e. Washington, British Columbia, Idaho, Montana) possess larger non-pruinose, shiny areas on these sternites (Fig. 21G). On Californian specimens these sternites are more pruinose (Fig. 21H). In Oregon there are apparent intermediates of the two states. Californian specimens can be, but are not always, weakly pruinose on the anepimeron, as opposed to the shiny anepimeron found in most. No other morphological characters to distinguish between the two populations were found. Two barcodes for S. brevicornis were recovered. One from an Alberta specimen and one from a California specimen. The two were 1.3% different, however, neither barcode was complete with the Albertan one missing data at both ends of the sequence and the Californian one missing the middle B fragment. Additional and complete sequences of both the northern and southern morphotypes of S. brevicornis are needed to determine whether a gradient exists or whether two discrete clusters are resolved.