Insects of Britain and Ireland: the genera of Syrphidae (hoverflies)
Adult flies. The flies Nomada-like; black to bluish-black or dark bronze, with yellow bands or spots; small to medium sized; 6–10(–11.5) mm long. Wings 5.5–9.25 mm long.
The head slightly 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. The eyes hairy, or bare. Antennae relatively short, drooping; with their bases well separated. The third antennal segment ovoid or orbicular. The antennal bristle dorsal; about as long as the third segment to much longer than the third segment; simple.
The humeri bare. The thorax pubescent without stiff bristles interspersed; plain; without longitudinal stripes. Wings plain; without a conspicuously dark stigma; 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 slightly diverging from the posterior wing margin to 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; oval. The lateral margins of the tergites exhibiting beaded rims (P. nigritarsis), or smoothly rolled over and without beading (usually). The male abdomen with 5 visible segments. The abdomen contrastingly patterned. The tergite patterning involving 2 to 4. The colour-patterned tergites marked with yellow. The dorsum of tergite 2 exhibiting a wineglass-shaped black area. The dorsum of tergite 3 with a sunglasses-shaped pale partially-interrupted pale band, or 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 entire, or medianly interrupted and partially interrupted (those on tergites 3 & 4 sometimes only partially interrupted); narrow to wide. The spiracles of the third abdominal segment borne in the middle of each side.
Larvae and pupae. The larvae scarcely tapering, or slightly tapering anteriorly and posteriorly from the middle; posteriorly blunt and tail-less; flattened (beneath - hemispherical in section); longitudinally striped, or not longitudinally striped (with light longitudinal stripes or dark chevrons); patterned; translucent, or not translucent; with dorsal projections; mouth with a triangular sclerite on either side; anal segments without lappets. The larvae predatory (most on pine adelgids and aphids, but P. punctulatus on ranges to Rosa and Fagus, while P. nigritarsis feeds exclusively on eggs, larvae and pupae of chrysomelids on Alnus and Salix).
Classification. Subfamily Syrphinae; tribe Syrphini.
British representation. 6 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’.