Insects of Britain and Ireland: the genera of Syrphidae (hoverflies)
Adult flies. The flies muscid-like; blackish; small; 5–6 mm long. Wings 6–7.5 mm long (i.e., relatively long-winged).
The head 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 (covered in long, drooping shaggy hairs); without a central knob; not elongated horizontally into a cone as long as the rest of the head. The eyes hairy. Antennae relatively short, drooping; with their bases approximated; black. The third antennal segment ovoid or orbicular. The antennal bristle dorsal; simple (bare).
The humeri hairy, and readily visible behind the head. The thorax pubescent without stiff bristles interspersed; plain; without longitudinal stripes. The scutellum black. Wings plain (grey, yellowish in front); without a conspicuously dark stigma (but the stigma conspicuously yellow); without black flecks along the hind edges; divergent in repose; apparently without 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 well above the base; bent at a sharp angle; 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 slightly wider than the thorax to about the same width as the thorax; ovate (to almost orbicular). The male abdomen with 4 visible segments. The abdomen not contrastingly patterned. The spiracles of the third abdominal segment borne at or near the anterior corner of each side.
Larvae and pupae. The larvae shortly tailed (?). The larvae saprophagous; in rot-holes and in decaying sap under loose bark (in decaying sap, in coniferous and hardwood trees).
Classification. Subfamily Milesiinae; tribe Merodontini.
British representation. 1 species in Britain (P. anthracina). A rarity, recorded from southern and midlands England.
Illustrations. • P. anthracina: Verrall. • 18 genera (from Walker).
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. delta-intkey.com’.