Platycheirus granditarsus explained

Platycheirus granditarsus, the Hornhand Sedgesitter, is a species of hoverfly. It is found in many parts of Britain North America and Europe. Typical habitat includes marshy meadows and ditches, where it can be found between May and October, though it is at its commonest between July and September. The most distinctive feature of this fly is the red-orange abdomen most easily seen as it takes off or alights.^{[1] [2] [3]}

Description

For terminology Speight key to genera and glossary

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HeadThe face is nearly vertical and the anterior oral margin is produced forward. It is shining, with silver pollinosity present only at lateral edges. The tubercle is somewhat large and abruptly pointed. The vertex is narrow, approximately two times as wide as the ocellar triangle. The antenna is black.

ThoraxThe thorax is shining to subshining black and the pile is white or pale yellow. The longest scutellar pile is approximately equal in length to the arista, while other thoracic pile is half as long.

AbdomenFor male specimens, the abdomen is oval, with extensive orange areas. Segment 2 usually has only the anterior and lateral edges black, sometimes with a median black line. Segment 3 has only posterolateral edges black, while segment 4 usually has a basal half that is black, occasionally with a median black line that divides the orange anterior half of the segment into two large spots. Segment 5 is dark and unmarked. The surstylus has a poorly developed basal process. external images

For female specimens, the abdomen is broadly oval, with orange areas similar to males. Segment 2 usually has all edges black, sometimes with a median black line. Segment 3 has a complete posterior black band and sometimes also a median black band that divides the orange area into two spots. Segment 4 usually has a basal half that is black, often with a median black line that divides the orange anterior half of the segment into two large spots. Segment 5 has anterior orange spots.

WingsThe wing is darkened, entirely microtrichose.

LegsThe legs are mostly dark, with broad apices of femora and bases of tibiae pale. The fore femur has short, stiff black setae spaced irregularly on the anteroventral and posteroventral surface. The first fore tarsomere has a large, anterior triangular process on the apical half. The first 4 tarsomeres of the mid leg are strongly flattened, each with a broad, apically rounded process which are progressively shorter from the first to third tarsomere.^[4] External images See references for determination.^{[5] [6] [7] [8]}

Distribution

Palearctic

Fennoscandia south to France and the Alps, Ireland east through Northern Europe and Central Europe into European Russia then across Siberia and the Russian Far East to the Pacific coast. Nearctic: Alaska to Quebec and south to Colorado.^{[9] [10] [11]}

Biology

Habitat: humid grassland subject to flooding, marsh, fen, edges of raised bogs. Flies May to September.^[12] It flies May to August.

Notes and References

1. Book: Ball, S.G. . Morris, R.K.A. . Provisional atlas of British hoverflies (Diptera, Syrphidae) . 2000 . Biological Record Centre . Monks Wood, UK . 1-870393-54-6 . 167 pages .
2. Book: Morris, Roger K.A. . 1999 . Hoverflies of Surrey . Surrey Wildlife Trust. 0-9526065-3-4 . 244.
3. Book: Stubbs, Alan E. . Falk, Steven J. . amp . 1983 . British Hoverflies: An Illustrated Identification Guide . British Entomological & Natural History Society. 253, xvpp.
4. Young . Andrew D . 2012 . A revision of the Nearctic species of Platycheirus Lepeletier and Serville (Diptera: Syrphidae) . master of SCIENCE . University of Guelph . 2012-05-09 .
5. Van Veen, M. (2004). Hoverflies of Northwest Europe: identification keys to the Syrphidae. 256pp. KNNV Publishing, Utrecht.addendum.
6. Van der Goot, V.S. (1981). De zweefvliegen van Noordwest - Europa en Europees Rusland, in het bijzonder van de Benelux. KNNV, Uitgave no. 32: 275pp. Amsterdam.
7. Bei-Bienko, G.Y. & Steyskal, G.C. (1988). Keys to the Insects of the European Part of the USSR, Volume V: Diptera and Siphonaptera, Part I. Amerind Publishing Co., New Delhi. .
8. Coe, R.L. (1953). "Diptera: Syrphidae". Handbks. Ident. Br. Insects 10(1): 1-98. R. Ent. Soc. London. pdf.
9. [Fauna Europaea]
10. Peck, L.V. (1988). "Syrphidae". In: Soos, A. & Papp, L. (eds.). Catalogue of Palaearctic Diptera 8: 11-230. Akad. Kiado, Budapest.
11. Book: Vockeroth . J.R. . 1992 . The Flower Flies of the Subfamily Syrphinae of Canada, Alaska, and Greenland (Diptera: Syrphidae). Part 18. The Insects and Arachnids of Canada . 1–456 . Canadian Government Pub Centre . Ottawa, Ontario . 0-660-13830-1.
12. Speight . M.C.D. . 2011 . Species accounts of European Syrphidae (Diptera) . Syrph the Net, the database of European Syrphidae . 65 . 285pp .