Insects of Britain and Ireland: the genera of Syrphidae (hoverflies)
Melithreptus Loew, Melitrophus.
Adult flies. The flies sometimes somewhat cephid sawfly-like, or sphecid wasp-like (often, cf. Cerceris, Crossocerus, Ectemnius); black with yellow markings; minute to medium sized; (5–)7–10(–12) mm long. Wings 4.25–7 mm long.
The head wider than the thorax, or wider than the thorax to about the same width as the thorax. The face ground-coloured at least part yellow; not flat or retreating between antennae and mouth; not elongated horizontally into a cone as long as the rest of the head. The eyes depicted as bare. Antennae relatively short, drooping; with their bases well separated; yellowish (yellow), or tawny. The third antennal segment ovoid or orbicular. The antennal bristle dorsal; simple (almost bare).
The humeri bare (and exposed). The thorax pubescent without stiff bristles interspersed; patterned (with yellow); with longitudinal stripes. The thoracic striping lateral only; exhibiting sharply defined, yellow lateral lines. The scutellum at least partly yellow. Wings plain (rather short and narrow, almost colourless to slightly grey); without a conspicuously dark stigma; without black flecks along the hind edges; 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; without a backwardly projecting, incomplete transverse veinlet. 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 slightly stepped to strongly stepped. The upper outer marginal cross-vein conspicuously bent near the base the base; not re-entrant. The alula distinct. The thoracic squamae without long hairs dorsally. The anterior anepisternum bare.
The abdomen about the same width as the thorax to narrower than the thorax (narrower in males); narrowly oval, or oblong, or more or less fusiform, or linear (narrower in males, sometimes waisted). The lateral margins of the tergites smoothly rolled over and without beading. The abdomen with 7 segments apparent. The male abdomen with 5 visible segments. The abdomen contrastingly patterned. The tergite patterning involving 2 to 5. The colour-patterned tergites marked with yellow. The interrupted band on tergite 2 reduced to small paired spots, or not reduced to small spots. The tergite bands medianly interrupted, or medianly interrupted and entire, or medianly interrupted, partially interrupted, and entire; narrow, or wide. The spiracles of the third abdominal segment borne in the middle of each side.
Larvae and pupae. The larvae tapering anteriorly and posteriorly from the middle (the body covered with dome-shaped papillae); posteriorly blunt and tail-less; scarcely flattened; green; longitudinally striped to not longitudinally striped (the pale dorsal stripes can be inconspicuous); bright green, patterned; mouth with a triangular sclerite on either side; anal segments without lappets. The larvae predatory (associated with aphids and other Homoptera on ground level plants).
Classification. Subfamily Syrphinae; tribe Syrphini.
British representation. 11 species in Britain.
Illustrations. • S. scripta: Verrall. • S. rueppellii: Verrall. • 18 genera (from Walker). • S. scripta, with assorted other Syrphidae (adult forms).
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’.