Chalcosyrphus

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This pretty little syrphid fly, Chalcosyrphus piger (or pigra), was displaying and/or basking from the railing of my deck. These flies are said to be "hilltoppers", that is, they gather at high places for mating, with males tending to stake out territories. These flies are all dark except for the bright red abdomen and are said to be Batesian mimics of spider wasps with this pattern, esp. genus Astata. Length about 10 mm.Identification as to species level in this genus is tough, but see the BugGuide page linked above, and especially this plate from Syrphidae of Ontario. Note short appressed (not erect) hairs on thorax, tarsi all black. Also, this is a common species listed in the North Carolina State University entomology collection, so I think I've got this one.

This pretty little syrphid fly, Chalcosyrphus piger, was displaying and/or basking from the railing of my deck. These flies are said to be "hilltoppers", that is, they gather at high places for mating, with males tending to stake out territories. These flies are all dark except for the bright red abdomen and are said to be Batesian mimics of spider wasps with this pattern, esp. genus Astata. (See adjacent lateral view for comments on ID.) Length about 10 mm.

WWT Knapp and Papermill Reserve Worcs. SO74925173

SO748520. WWT The Knapp Reserve, Worcs.

WWT Knapp and Papermill Reserve Worcs. SO74925173From Diptera info:-Post subject: Data sheet from National Review of Diptera, Falk, 1991Reply with quoteDatasheet from the Review of Scarce and Threatened Diptera, Falk (1991). CHALCOSYRPHUS EUNOTUS (Loew) VULNERABLE DISTRIBUTION Only six known sites within the Welsh Borders and southern England: Knapp and Paper Mill N.R., Alfrick (1986 and 1987), Shrawley Wood, nr Stourport (1986 and 1987) and an unspecified site in the Wyre Forest (1971), all in Worcestershire; Cothill NNR, Berkshire (1953); Ledbury, Herefordshire (1899) and Bracketts Coppice, Dorset (1987). HABITAT Old broadleaved woodlands with streams. ECOLOGY Larvae probably develop in dead wood. Most records apply to adults sitting on partly submerged logs, strongly suggesting that the larvae live in semi-submerged wood. Adults recorded in May and June. STATUS Four post 1960 sites. It may prove to be more widespread along the Welsh borders with more thorough searching and the Dorset record is encouraging. This species is likely to remain vulnerable through the apparently specialised choice of breeding site. THREAT Unclear, but probably the clearance of old woodland sites and removal of dead wood, especially semi-submerged logs. MANAGEMENT Maintain known sites as broadleaved woodland, retaining any semi-submerged logs and ensure a continuity of dead wood in future by maximising the number of diseased and post mature trees

Chalcosyrphus chalybeusNew Paltz, New York (June 28, 2010)

SO748520. WWT The Knapp Reserve, Worcs.

SO748520. WWT The Knapp Reserve, Worcs.

Crichton, Scotland, United Kingdom