Insects of Britain and Ireland: the genera of Syrphidae (hoverflies)
Syrphus p.p.; Fagisyrphus, Stenosyrphus.
Adult flies. The flies Nomada-like (?), or sphecid wasp-like (cf. Crossocerus quadrimaculatus); black to dark bronze, usually with pale abdominal markings that are whitish rather than yellow; small to medium sized; 7–11 mm long. Wings 5.75–9(–10) mm long.
The head wider than the thorax to about the same width as the thorax. The face entirely dark in ground colour (black); not flat or retreating between antennae and mouth; with a central knob; not elongated horizontally into a cone as long as the rest of the head. The frons not inflated; smooth. The eyes hairy, or bare; not rimmed along their facial borders for much of the height of the face. Antennae relatively short, drooping; with their bases well separated; black. The third antennal segment ovoid or orbicular. The antennal bristle dorsal; much longer 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 (pale grey in M. umbellatorum); without a conspicuously dark stigma (the stigma grey or pale brown); exhibiting tiny uniformly spaced black flecks along the hind edges (M. cincta), or without black flecks along the hind edges (?); 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 more or less parallel with the posterior wing margin. The upper and lower outer marginal cross veins more or less continuous to slightly stepped (?). The upper outer marginal cross-vein gently curved, or conspicuously bent near the base the base (?); not re-entrant. The alula distinct. The thoracic squamae without long hairs dorsally. The hind legs black or at most narrowly pale at the knee. The metasternum entire, broad over its whole length. The anterior anepisternum bare.
The abdomen about the same width as the thorax to narrower than the thorax; almost linear, or oval, or more or less fusiform, or ovate. The lateral margins of the tergites smoothly rolled over and without beading. The abdomen with 5–6 segments apparent. The male abdomen with 5 visible segments. The abdomen contrastingly patterned, or not contrastingly patterned (female M. quadrimaculata). The tergite patterning involving 2 to 4, or 3 to 4. The colour-patterned tergites marked with whitish (often), or yellow to tawny. The interrupted band on tergite 2 reduced to small paired spots (these very triangular). The dorsum of tergite 2 exhibiting a wineglass-shaped black area, or without a wineglass-shaped black area. The tergite bands medianly interrupted; narrow. 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; posteriorly blunt and tail-less; flattened (the body sub-triangular in section, the flattened lateral margins smooth); green (e.g., M. cincta), or not green; longitudinally striped, or not longitudinally striped; variously patterned (e.g., chevrons or rectangular blocks); with dorsal projections, or dorsally smooth, without projections; mouth with a triangular sclerite on either side; anal segments without lappets. The larvae predatory (probably all aphidivorous, many being species-specific but the genus associated with a very wide range including those of conifers, hardwoods and dicot herbs).
General comments. Medium sized flies, with a dark, elongate abdomen that is marked in most species with rather small spots, these whitish rather than yellow.
Classification. Subfamily Syrphinae; tribe Syrphini.
British representation. 9 species in Britain.
Illustrations. • M. arctica, M. barbifrons, M. compositarum, M. labiatarum: Verrall. • M. quadrimaculata, male (Verrall). • M. barbifrons, Epistrophe grossulariae, Syrphus ribesii and Syrphus torvus (thoracic squamae).
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’.