Insects of Britain and Ireland: the genera of Syrphidae (hoverflies)
Adult flies. The flies bumblebee-like (V. bombylans, cf. assorted British Bombus spp.), or vespid wasp-like (V. zonaria), or vespid wasp-like and hornet-like (V. inanis); black, black and white, black and yellow or black and orange; medium sized to large; 11–20 mm long. Wings 8–19.5 mm long.
The head about the same width as the thorax to less wide than the thorax. The face not flat or retreating between antennae and mouth; with a central knob; more or less produced below and extending beyond the antennae, or not extending below beyond the antennae. The eyes hairy, or bare. Antennae relatively short, drooping; with their bases approximated; ferruginous, or black and ferruginous. The third antennal segment ovoid or orbicular. The antennal bristle dorsal; much longer than the third segment; plumose.
The humeri hairy, and readily visible behind the head. The thorax patterned (by hair colours), or plain; with longitudinal stripes, or without longitudinal stripes. The scutellum pale brownish, ferrugineous or tawny (V. inflata), or black (piceous, in V. bombylans and V. pellucens). Wings patterned (palely tinted proximally, with a dark area extending halfway across the wing from the stigma and darkened near the wing-tip), or patterned to plain (the discal darkening lacking in V. lappona); with a conspicuous dark stigma, or without a conspicuously dark stigma; divergent in repose. Wing veins R2+3 and R4+5 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 to conspicuously bent near the base the base; re-entrant. The alula distinct.
The abdomen much wider than the thorax; obovate (to almost orbicular); conspicuously furry to not conspicuously furry; contrastingly patterned (sometimes colour-tailed only, with the posterior segments black, white or tawny). The patterning attributable to the furry hair coat (e.g., V. bombylans), or not attributable only to the hair coat (e.g., V. inanis, V. zonaria). The tergite patterning involving 2 to 4, or 2, or 4. The colour-patterned tergites marked with yellow, or tawny. The tergite patterning confined to tergite 2, or not confined to one tergite. The tergite bands narrowly medianly interrupted, or medianly interrupted and partially interrupted, or entire; narrow to wide.
Larvae and pupae. The larvae somewhat broader posteriorly, tapered to the head, or tapering anteriorly and posteriorly from the middle; posteriorly blunt and tail-less; scarcely flattened to flattened (exhibiting well developed prolegs with long crochets, also conspicuous transverse rows of setae and long, pointed lateral projections along the lateral margins, except in V. inanis, which is smooth bodied and more flattened); plain; with conspicuous lateral projections, or laterally smooth; without thoracic hooks; mouth without triangular sclerites; anal segments with lappets. The larvae saprophagous (V.inflata, recorded from a sap run on Quercus), or predatory (the other species found in nests of social vasps, consuming larvae, pupae, corpses and probably waste materials).
Classification. Subfamily Milesiinae; tribe Volucellini.
British representation. 5 species in Britain.
Illustrations. • Volucella inflata (Inflated Hover-fly: B. Ent. 452). • Volucella inflata: B. Ent. 452, legend+text. • Volucella inflata: B. Ent. 452, text cont.. • V. bombylans and B. inanis, with Chrysotoxum festivum. • V. bombylans and V. inflata: Verrall.
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’.