Insects of Britain and Ireland: the genera of Syrphidae (hoverflies)
Formerly Syrphus p.p.
Adult flies. The flies Nomada-like; typically mainly black and yellow, but dark forms occur; medium sized; 10.5–12.5 mm long. Wings 6–10.25 mm long.
The head about the same width as the thorax. The face ground-coloured at least part yellow; 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 smooth. The eyes bare. Antennae relatively short, drooping; with their bases well separated; black and ferruginous. The third antennal segment ovoid or orbicular. The antennal bristle dorsal; simple (bare).
The humeri bare. The thorax pubescent without stiff bristles interspersed; plain. The scutellum brownish, ferrugineous or tawny (dull tawny, according to Walker). Wings plain (colourless with black veins and a tawny-brownish stigma); with a conspicuous dark stigma; exhibiting tiny uniformly spaced black flecks along the hind edges; divergent 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 slightly stepped to strongly stepped. The upper outer marginal cross-vein conspicuously bent near the base the base; not re-entrant. The alula distinct. The thoracic squamae without long hairs dorsally. The anterior anepisternum at least partly pilose.
The abdomen about the same width as the thorax; depressed, shortly to elongate- oval, or oblong. 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. The tergite patterning involving 2 to 4 (commonly with very unusual double black banding of the adults tergites 3 & 4). The colour-patterned tergites marked with yellow. The dorsum of tergite 2 exhibiting a wineglass-shaped black area, or without a wineglass-shaped black area. The tergite bands medianly interrupted, partially interrupted, and entire, or medianly interrupted and entire (that on tergite 2 always widely interrupted); narrow and wide (usually 2 per segment). The spiracles of the third abdominal segment borne in the middle of each side.
Larvae and pupae. The larvae somewhat tapering anteriorly and posteriorly from the middle; posteriorly blunt and tail-less; scarcely flattened; green; more or less patterned (being medianly green dotted with white, but translucent anteriorly and posteriorly); translucent; dorsally smooth, without projections; mouth with a triangular sclerite on either side; anal segments without lappets. The larvae predatory (aphidivorous, on a wide range of arboreal and ground-layer species).
Classification. Subfamily Syrphinae; tribe Syrphini.
British representation. 1 species in Britain (E. balteatus). The most frequently recorded hoverfly throughout the British Isles.
Illustrations. • E. balteatus: Verrall. • E. balteatus, with assorted other Syrphidae (adult forms).
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’.