Insects of Britain and Ireland: the genera of Syrphidae (hoverflies)

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L. Watson and M. J. Dallwitz

Criorhina Meigen

Criorrhina, Penthesilia.

Adult flies. The flies very hairy-bodied and bumblebee-like (C. berberina, C. floccosa and C. ranunculi, cf. assorted British Bombus spp.), or hivebee-like (the less hairy-bodied C. asilica); black, but often furry-hairy with long tawny hairs; medium sized to large; 10.3–16 mm long. Wings 8–14 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 to well below the level of the eyes); with a central knob to without a central knob (with a slight prominence ony). The eyes depicted as bare. Antennae relatively short, drooping; with their bases well separated; black, or ferruginous, or black and ferruginous. The third antennal segment ovoid or orbicular (shorter than wide). 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. Wings plain (colourless or colourless slightly clouded with grey, pale grey, pale grey clouded with black in the middle, or nearly colourless with tawny tinges); 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. 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. The upper outer marginal cross-vein gently curved; not re-entrant. The alula distinct.

The abdomen wider than the thorax to about the same width as the thorax, or about the same width as the thorax to narrower than the thorax; oval, or obovate (sometimes more or less orbicular), or oblong. The male abdomen with 4 visible segments. The abdomen conspicuously furry; contrastingly patterned (sometimes whitish- or tawny-tailed), or not contrastingly patterned. The patterning attributable to the furry hair coat, or not attributable only to the hair coat (C. asilica). The tergite patterning involving 2 and 3. The tergite bands narrow. 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 (shortly so). The anal segment tapered gradually to the spiracular process. The larvae flattened (the prolegs detectable but reduced); pallid, plain; with hooks on the thorax (a cow-horn shaped pair, directed laterally behind the anterior spiracles); mouth without triangular sclerites; anal segments with lappets. The larvae saprophagous; in rot-holes, in rotten wood, and in decaying tree roots.

Classification. Subfamily Milesiinae; tribe Xylotini.

British representation. 4 species in Britain.

Illustrations. • C. ranunculi male, with Brachypalpoides, Eristalis and Xylota. • C. asilica and C. floccosa: Verrall. • 15 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.’.