Insects of Britain and Ireland: the genera of Syrphidae (hoverflies)
Adult flies. The flies muscid-like (cf. Scatophagidae), or pamphiliid sawfly-like (cf. Neurotoma); orange-brown: the thorax ground-coloured orange, the abdomen entirely or partly orange or brown; 10–12 mm long. Wings 8.25–9.75 mm long.
The head less wide than the thorax. The face flat or concave in the region between the antennae and the mouth (concave, leading smoothly to the projecting margin of the mouth); with a central knob (male), or without a central knob (female). The eyes bare. Antennae relatively short, drooping; with their bases well separated. The third antennal segment ovoid or orbicular. The antennal bristle apical; much longer than the third segment; plumose.
The humeri hairy, and readily visible behind the head. The thorax pubescent with stiff bristles interspersed; patterned, or plain (?); with longitudinal stripes (these pale), or without longitudinal stripes (?). The scutellum brownish, ferrugineous or tawny, or black. Wings plain; without a conspicuously dark stigma. 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. Vein R bearing bristles. 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 strongly stepped. The upper outer marginal cross-vein conspicuously bent well above the base; curved on the bend; not re-entrant. The alula distinct.
The abdomen about the same width as the thorax to narrower than the thorax; narrowly oval to more or less fusiform, or ovate; not contrastingly patterned (but sometimes with indistinct paired pale brown spots on tergites 3 and 4).
Larvae and pupae. The larvae tapering anteriorly and posteriorly from the middle (with lateral projections); posteriorly blunt and tail-less; flattened (prolegs weakly developed); very dark, plain; with conspicuous lateral projections; without thoracic hooks; anal segments with lappets. The larvae saprophagous; in sap runs and in decaying sap under loose bark (on aspens).
General comments. The colouring of thorax and abdomen as described by Stubbs and Falk compares alarmingly poorly with the illustration they provide.
Classification. Subfamily Milesiinae; tribe Chrysogastrini.
British representation. 1 species in Britain (H. ferruginea). Known in Britain only from a few locations in the Scottish Highlands.
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’.