Insects of Britain and Ireland: the genera of Syrphidae (hoverflies)
Adult flies. The flies entirely black, or the abdomen partly or mostly red; minute to small; 3.5–7 mm long. Wings 3.5–6 mm long.
The head somewhat wider than the thorax. The face ground-coloured at least part yellow (patterned yellow and black); not flat or retreating between antennae and mouth; 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, or black and ferruginous. The third antennal segment ovoid or orbicular. The antennal bristle dorsal; shorter than the third segment; simple (bare).
The humeri bare. The thorax pubescent without stiff bristles interspersed; plain; without longitudinal stripes. The scutellum black. Wings plain (rather small, colourless or slightly grey); without a conspicuously dark stigma; incumbent and almost parallel in repose. 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. 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; not re-entrant. The alula distinct to indistinct.
The abdomen wider than the thorax to about the same width as the thorax; convex or depressed only basally, oval, or obovate (e.g., P. albifrons), or more or less fusiform, or oblong (to somewhat waisted in the middle, e.g., P. haemorrhous, E. tibialis). The male abdomen with 5 visible segments (with segment 1 unusually well developed, extending well beyond the scutellum). The abdomen contrastingly patterned (female P. albifrons), or not contrastingly patterned (P. haemorrhous, male P. albifrons). The tergite patterning involving 2 and 3 (when present). The colour-patterned tergites marked with when present, tawny, or red (duskily so). The spiracles of the third abdominal segment borne in the middle of each side.
Larvae and pupae. The larvae broader posteriorly, tapered to the head (to 8 mm long,); posteriorly blunt and tail-less; flattened (oval in section, posteriorly flattened); brown, patterned (mottled white and darker brown); with dorsal projections; with conspicuous lateral projections; mouth with a triangular sclerite on either side; anal segments without lappets. The larvae predatory (on root aphids).
General comments. The face arched and not hollowed beneath the frontal prominence, patterned yellow and black; wings longer than the abdomen.
Classification. Subfamily Syrphinae; tribe Paragini.
British representation. 4 species in Britain.
Illustrations. • Paragus haemorrhous: B. Ent. 593. • Paragus haemorrhous: B. Ent. 593, legend+text. • Paragus haemorrhous: B. Ent. 593, text, cont.. • P. tibialis: 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’.