Insects of Britain and Ireland: the genera of Syrphidae (hoverflies)
Adult flies. The flies megachilid bee-like (cf. Osmia bicolor and O. aurulenta); black with a red tail; small to medium sized; 10–12 mm long. Wings 8–9.5 mm long.
The head about the same width as the thorax. The face ground-coloured at least part yellow. Antennae relatively short, drooping. The third antennal segment ovoid or orbicular. The antennal bristle dorsal; much longer than the third segment; simple.
The humeri hairy, and readily visible behind the head. The thorax shortly pubescent; plain. The scutellum flat, with a well defined edge. Wings plain; 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 at or beyond 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 markedly diverging from the posterior wing margin to slightly diverging from 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 abdomen wider than the thorax (in the female), or about the same width as the thorax (in the male); oval, or ovate, or oblong, or obovate; conspicuously furry; contrastingly patterned (distinctively reddish-tailed). The patterning not attributable only to the hair coat.
Larvae and pupae. The larvae broader posteriorly, tapered to the head; tailed (?); flattened. The larvae semi-aquatic, or non-aquatic; saprophagous (?); in rot-holes and in decaying sap under loose bark, or in decaying tree roots (associated with rotten heartwood in Pinus, also with water-filled tree rot holes and perhaps decaying roots).
Classification. Subfamily Milesiinae; tribe Xylotini.
British representation. 1 species in Britain (B. fallax). Confined to the Scottish Highlands.
Illustrations. • B. fallax: 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’.