Insects of Britain and Ireland: the genera of Syrphidae (hoverflies)
Formerly Criorhina p.p.
Adult flies. The flies in appearance hivebee-like, or resembling Colletes (but different in behaviour, often being found running over leaves and bark); black or blackish bronze; 11–13.6 mm long. Wings 8.5–10.75 mm long.
The head about the same width as the thorax to less wide than the thorax. The face flat or concave in the region between the antennae and the mouth (descending well below the level of the eyes); without a central knob; impressed. Antennae relatively short, drooping; with their bases approximated; black and tawny. 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 shaggy with soft hair; plain; without longitudinal stripes. The scutellum somewhat convex, with undefined edge; black. Wings scarcely patterned to plain (almost colourless, with a slight tawny tinge along the front, a narrow band on the transverse veins in the middle, and a paler and more diffuse brown spot on the disc towards the tip); 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 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 more or less parallel with the posterior wing margin. The upper outer marginal cross-vein conspicuously bent near the base the base; not re-entrant. The alula distinct.
The abdomen about the same width as the thorax to narrower than the thorax (in the male), or wider than the thorax to about the same width as the thorax (in the female); about 6.65–7; oval (in the male), or ovate (in the female). The male abdomen with 4 visible segments. The abdomen not conspicuously furry; not contrastingly patterned (but sometimes orange-ish at the rear of the tergites, and/or laterally on tergites 2 and 3). The spiracles of the third abdominal segment borne at or near the anterior corner of each side.
Larvae and pupae. The larvae tapering posteriorly; tailed. The anal segment tapered gradually to the spiracular process. The larvae flattened; brown, plain; with hooks on the thorax (with one lateral to each anterior spiracle and another below this); mouth without triangular sclerites; anal segments with lappets. The larvae saprophagous; in rot-holes and in decaying sap under loose bark (on deciduous trees).
General comments. The thorax long-haired, and the hind femur swollen.
Classification. Subfamily Milesiinae; tribe Xylotini.
British representation. 1 species in Britain (B. laphriformis).
Illustrations. • Brachypalpus laphriformis, male hind leg (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’.