Insects of Britain and Ireland: the genera of Syrphidae (hoverflies)
Adult flies. The flies variously bumblebee-like (C. illustrata), or resembling a potter bee (C. aenea, C. rufa, etc.), or resembling a mining bee (C. albipila, cf. Andrena apicata), or megachilid bee-like, or halictid bee-like (C. impressa, etc.), or muscid-like, or not suggestive of mimicry; blackish, rarely marked with grey; small to medium sized; 5.6–13.6 mm long. Wings (4.75–)6–10.75 mm long.
The head about the same width as the thorax to less wide than the thorax. The face entirely dark in ground colour; not flat or retreating between antennae and mouth; with a central knob (always or nearly always?); produced below and extending beyond the antennae, or not extending below beyond the antennae; not elongated horizontally into a cone as long as the rest of the head. The frons not inflated; pitted or channelled. The eyes hairy (often), or bare; rimmed along their facial borders for much of the height of the face. Antennae relatively short, drooping; with their bases well separated (seated on a slight projection); black, or ferruginous, or black and ferruginous (the black component often piceous). The third antennal segment ovoid or orbicular. The antennal bristle dorsal; much longer than the third segment; simple (bare or pubescent).
The humeri hairy, and readily visible behind the head. The thorax plain; without longitudinal stripes. The scutellum sometimes tawny. Wings patterned, or plain (mostly grey to colourless and unpatterned, sometimes tinged brown or tawny along the fore border, occasionally with a large brown spot extending from the mid-fore border to the disc); 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. 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 more or less continuous to strongly stepped. The upper outer marginal cross-vein gently curved to conspicuously bent near the base the base; not re-entrant. The alula distinct.
The abdomen wider than the thorax to narrower than the thorax; oval, or ovate, or oblong, or obovate, or more or less fusiform, or clavate, or linear; with 5–6 segments apparent. The male abdomen with 4 visible segments. The abdomen conspicuously furry to not conspicuously furry; contrastingly patterned, or not contrastingly patterned. The patterning when manifest, attributable to the furry hair coat. Tergites 2–4 equally shiny-metallic all over, without dull patches. The spiracles of the third abdominal segment borne at or near the anterior corner of each side.
Larvae and pupae. The larvae broader posteriorly, tapered to the head to tapering anteriorly and posteriorly from the middle; posteriorly blunt and tail-less; flattened; plain (usually brown); without thoracic hooks; mouth without triangular sclerites; anal segments with lappets. The larvae variously phytophagous, or mycophagous; feeding on (when phytophagous) Alliaceae, or Amaryllidaceae, or Compositae, or Crassulaeae, or Iridaceae, or Primulaceae, or Ranunculaceae, or Rosaceae, or Scrophulariaceae, or Umbelliferae (the British phytophage representatives seemingly confined to Dicots, feeding in stems or roots or some mining leaves); recorded in fruit-bodies of (when mycophagous) Amanita, or Boletus, or Leccinum, or Suillus, or polypores.
General comments. The adults sometimes but not always tawny-gingery hairy and bumblebee-like, but often much more slender and only inconspicuously hairy; never greenish or shiny purplish as in Lejogaster, Chrysogaster and Orthonevra, nor with the medianly dull but laterally shiny abdomen of Melanogaster and Orthonevra.
Classification. Subfamily Milesiinae; tribe Cheilosiini.
British representation. 35 species in Britain.
Illustrations. • C. illustrata, male (with Merodon and Platycheirus). • C. bergenstammi, C. fraterna, C. illustrata, C. impressa, C. nebulosa, C. soror: Verrall. • C. cyanocephala, C. longula, C. pagana, C. scutellata, C. soror, C. variabilis: Verrall. • 18 genera (from Walker).
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’.