Insects of Britain and Ireland: the genera of Syrphidae (hoverflies)
Syrphus p.p., Episyrphus p.p.
Adult flies. The flies sphecid wasp-like (cf. Crossocerus quadrimaculatus); black with yellow markings; small to medium sized; 9–11.5 mm long. Wings 7–9.75 mm long.
The head wider than the thorax to 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 not inflated; 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; without longitudinal stripes. The scutellum at least partly yellow. Wings plain (slightly grey, with black veins); at least sometimes with a conspicuous dark stigma; exhibiting tiny uniformly spaced black flecks along the hind edges (Coe, 1953); 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. The lower outer marginal vein slightly diverging from the posterior wing margin. The thoracic squamae without long hairs dorsally. The anterior anepisternum at least partly pilose.
The abdomen about the same width as the thorax to narrower than the thorax; oblong, or obovate, or more or less fusiform, or linear. The lateral margins of the tergites smoothly rolled over and without beading. The male abdomen with 5 visible segments. The abdomen contrastingly patterned. The tergite patterning involving 2 to 4, or 2 to 5. The colour-patterned tergites marked with yellow, or tawny. The dorsum of tergite 2 exhibiting a wineglass-shaped black area, or without a wineglass-shaped black area. The dorsum of tergite 3 with a brassiere-shaped pale partially-interrupted band, or with neither a sunglasses-shaped nor a brassiere-shaped partially-interrupted pale band. The tergite bands medianly interrupted, or medianly interrupted and partially interrupted, or medianly interrupted and entire (always interrupted on tergite 2); narrow, or wide, or narrow and wide. 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; more or less patterned, or plain (?); translucent, or not translucent; dorsally smooth, without projections; mouth with a triangular sclerite on either side; anal segments without lappets. The larvae predatory (associated with aphid colonies on divers herbaceous and woody Dicotyledons, also with psyllids).
Classification. Subfamily Syrphinae; tribe Syrphini.
British representation. 2 species in Britain.
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’.