Insects of Britain and Ireland: the genera of Syrphidae (hoverflies)

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L. Watson and M. J. Dallwitz

Trichopsomyia Williston

Pipiza p.p., Parapenium.

Adult flies. The flies black or bluish-black, some with yellow markings; minute to small; 5–8 mm long. Wings 4–6 mm long.

The head wider than the thorax to about the same width as the thorax. The face entirely dark in ground colour; flat or concave in the region between the antennae and the mouth; without a central knob (covered with long, drooping shaggy hairs). The eyes hairy. Antennae relatively short, drooping; with their bases well separated (seated on a prominent part of the frons); black. The third antennal segment ovoid or orbicular. The antennal bristle dorsal; simple (but quite hairy).

The humeri hairy, and readily visible behind the head. The thorax pubescent without stiff bristles interspersed; plain; without longitudinal stripes. The scutellum black. Wings patterned, or plain (grey, sometimes with a large, dark, indefinite grey spot extending from the yellow-brown stigma to mid-disc); without a conspicuously dark stigma; divergent in repose; with a vena spuria. Wing veins R2+3 and R4+5 not forming a closed cell. The anterior cross vein R-M in cell R5 crossing it before the middle of the adjoining discal cell. Vein R4+5 without a conspicuous curve projecting into the cell R5; without a backwardly projecting, incomplete transverse veinlet. Vein R without bristles. The lower outer marginal vein markedly diverging from the posterior wing margin. The upper and lower outer marginal cross veins strongly stepped. The upper outer marginal cross-vein conspicuously bent near the base the base; joining vein R4+5 almost at right angles, so that cell R5 is not extended towards the wing tip; not re-entrant. The alula distinct.

The abdomen about the same width as the thorax to narrower than the thorax; flattened, oval, or ovate; with tergites 2, 3 and 4 all more or less well developed; contrastingly patterned (in the female), or not contrastingly patterned. The tergite patterning involving 2 (i.e., in the female). The colour-patterned tergites marked with yellow. The tergite patterning confined to tergite 2. The interrupted band on tergite 2 reduced to small paired spots.

Larvae and pupae. The larvae broader posteriorly, tapered to the head; posteriorly blunt and tail-less; scarcely flattened to flattened (hemispherical); plain (uniformly translucent creamy white); translucent; dorsally smooth, without projections; mouth with a triangular sclerite on either side; anal segments without lappets. The larvae predatory (on Juncus-associated psillids).

Classification. Subfamily Milesiinae; tribe Pipizini.

British representation. 1 species in Britain (T. flavitarsis). Scottish Highlands to the English Midlands, Wales and Ireland.

Illustrations. • Trichopsomyia flavitarsis: B. Ent. 669. • Trichopsomyia flavitarsis: B. Ent. 669, legend+text. • Trichopsomyia flavitarsis: B. Ent. 669, text cont..

To view the illustrations with detailed captions, go to the interactive key. This also offers full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting or lacking specified attributes, and distributions of character states within any set of taxa.

Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 2003 onwards. Insects of Britain and Ireland: the genera of Syrphidae (hoverflies). Version: 28th July 2015.’.