Insects of Britain and Ireland: the genera of Syrphidae (hoverflies)
Formerly Chrysogaster p.p., Liogaster.
Adult flies. The flies somewhat muscid-like; shiny metallic green, unmarked; minute to small; 5–7 mm long. Wings 4.5–6.5 mm long.
The head wider than the thorax to about the same width as the thorax. The face entirely dark in ground colour; flat or concave in the region between the antennae and the mouth (concave, leading smoothly to the projecting margin of the mouth); without a central knob; not elongated horizontally into a cone as long as the rest of the head; without tubercles. The eyes bare. Antennae relatively short, drooping; with their bases well separated (seated on a tubercle); black. The third antennal segment ovoid or orbicular. The antennal bristle dorsal; simple (bare).
The humeri hairy, and readily visible behind the head. The thorax bare or finely pubescent?; plain; without longitudinal stripes. The scutellum flat, with a well defined edge. Wings plain (slightly grey); without a conspicuously dark stigma; 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. Vein R without bristles. 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 near the base the base; not re-entrant. The alula distinct.
The abdomen much wider than the thorax to about the same width as the thorax; oval, or ovate (depressed). The male abdomen with 4 visible segments. The abdomen with tergites 2, 3 and 4 all more or less well developed; not contrastingly patterned. 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 tapering posteriorly; tailed. The anal segment tapered gradually to the spiracular process (not rat-tailed). The larvae scarcely flattened; brown, plain; without thoracic hooks; mouth without triangular sclerites; anal segments with lappets. The larvae more or less aquatic; saprophagous; in decaying vegetation (and mud, in still and slow-moving water).
Classification. Subfamily Milesiinae; tribe Chrysogastrini.
British representation. 2 species in Britain.
Illustrations. • L. metallina: 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’.