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

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L. Watson and M. J. Dallwitz

Xanthandrus Verrall

Syrphus p.p.

Adult flies. The flies Nomada-like, or hornet-like; black or blackish with yellow to reddish-orange markings; small to medium sized; 10–12 mm long. Wings 8.75–11.5 mm long.

The head wider than the thorax. The face entirely dark in ground colour (black); not flat or retreating between antennae and mouth; not elongated horizontally into a cone as long as the rest of the head. The frons smooth. The eyes depected as bare. Antennae relatively short, drooping; with their bases well separated; black (piceous). The third antennal segment ovoid or orbicular. The antennal bristle dorsal; much longer than the third segment; simple (bare).

The humeri bare. The thorax pubescent without stiff bristles interspersed; plain; without longitudinal stripes. The scutellum aeneous (aeneous, according to Coe), or black (? - cf. van Veen’s key). Wings plain (slightly grey); with a conspicuous dark stigma (this unusually elongate); 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. The upper and lower outer marginal cross veins slightly stepped. The upper outer marginal cross-vein conspicuously bent near the base the base; not re-entrant. The alula distinct. The front tibiae and/or tarsi simple.

The abdomen wider than the thorax; depressed, more or less oval (but somewhat angular in the middle); with 5–6 segments apparent. The male abdomen with 5 visible segments. The abdomen contrastingly patterned. The tergite patterning involving 2 to 4. The colour-patterned tergites marked with yellow to tawny. The interrupted band on tergite 2 reduced to small paired spots. The dorsum of tergite 3 with a sunglasses-shaped pale partially-interrupted pale band, or with a brassiere-shaped pale partially-interrupted band, or with neither a sunglasses-shaped nor a brassiere-shaped partially-interrupted pale band. The tergite bands medianly interrupted, or medianly interrupted and entire, or medianly interrupted and partially interrupted (the band on tergite 2 reduced to a pair of spots, those on 3 and 4 widely interrupted or only partially so); narrow to wide. The spiracles of the third abdominal segment borne in the middle of each side.

Larvae and pupae. The larvae broader posteriorly, tapered to the head, or tapering anteriorly and posteriorly from the middle; posteriorly blunt and tail-less; scarcely flattened (oval in section); green; translucent green, patterned (with dark spots); translucent; mouth with a triangular sclerite on either side; anal segments without lappets. The larvae predatory (on larvae of yponomeutid and tortricid micro-lepidoptera).

Classification. Subfamily Syrphinae; tribe Bacchini.

British representation. 1 species in Britain (X. comtus). Recorded from southern England to N. Wales, southern Scotland and Ireland.

Illustrations. • X. comptus (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.’.