Insects of Britain and Ireland: the genera of Syrphidae (hoverflies)
Adult flies. The flies Nomada-like, or cephid sawfly-like (female C. scaevoides); black to dark bronze, banded or spotted yellow to grey; minute to small; 3–6.2 mm long. Wings 4–6.25 mm long.
The head wider than the thorax to about the same width as the thorax. The face with the lower half extending smoothly forwards; without a central knob; not elongated horizontally into a cone as long as the rest of the head. Antennae relatively short, drooping; black and tawny. The third antennal segment ovoid or orbicular. The antennal bristle dorsal; shorter than the third segment; simple.
The humeri hairy, and readily visible behind the head. The thorax plain; without longitudinal stripes. Wings plain; 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 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. The lower outer marginal vein markedly 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 to indistinct.
The abdomen slightly clavate, or oval, or more or less fusiform, or linear. The male abdomen with 4 visible segments. The abdomen contrastingly patterned. The tergite patterning involving 2 to 4. The colour-patterned tergites marked with whitish, or yellow. The tergite patterning not confined to one tergite. The interrupted band on tergite 2 reduced to small paired spots, or not reduced to small spots. The tergite bands medianly interrupted, or partially interrupted, or entire (sometimes only the proximal one is completely interrupted, sometimes some are only partly so); wide. The spiracles of the third abdominal segment borne at or near the anterior corner of each side.
Larvae and pupae. The larvae presumably detectably segmented (but no description seen).
General comments. A poorly known species, associated with conifers but the life cycle seems to be unknown. Wings somewhat peculiar, in being broadly rounded at the tip with the costa extending around the end..
Classification. Subfamily Milesiinae; tribe Pelecocerini.
British representation. 2 species in Britain.
Illustrations. • Characteristic antenna of C. scaevoides: 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’.