Insects of Britain and Ireland: the genera of Syrphidae (hoverflies)
Adult flies. The flies more or less vespid wasp-like (cf. Dolichovespula and Vespula); black with yellow to tawny markings; medium sized to large; 9–18 mm long. Wings 8.5–12.25 mm long.
The head about the same width as the thorax. The face ground-coloured at least part yellow; not flat or retreating between antennae and mouth; with a central knob; with tubercles; elongated and tuberculated. The eyes bare. Antennae relatively short, drooping; with their bases approximated (seated on a small tubercle); black. The third antennal segment ovoid or orbicular. The antennal bristle dorsal; much longer than the third segment; simple (bare or pubescent).
The humeri hairy, and readily visible behind the head. The thorax pubescent without stiff bristles interspersed; sometimes fairly inconspicuously patterned; not exhibiting a skull-like figure; with longitudinal stripes (the dorsal stripes whitish to pale yellowish). The scutellum somewhat convex, with undefined edge; brownish, ferrugineous or tawny (or ferrugineous). Wings plain (slightly grey or colourless); without a conspicuously dark stigma; divergent in repose, or divergent in repose to incumbent and almost parallel in repose. Wing veins R2+3 and R4+5 not forming a closed cell (but almost doing so, the veins converging at the wing margin). The anterior cross vein R-M in cell R5 crossing it at or beyond the middle of the adjoining discal cell (near the middle or somewhat beyond). Vein R4+5 with a conspicuous curve projecting into the cell R5; without a backwardly projecting, incomplete transverse veinlet. 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 (almost straight); not re-entrant. The alula distinct. The hind femur distally with neither a triangular plate nor a tooth.
The abdomen usually wider than the thorax, or about the same width as the thorax to narrower than the thorax (wider in the female); oval, or oblong, or obovate. The male abdomen with 4 visible segments. The abdomen contrastingly patterned. The tergite patterning involving 2 and 3 (usually), or 2 to 4. The colour-patterned tergites marked with yellow, or tawny. The tergite patterning not comprising obliquely longitudial marks. The dorsum of tergite 2 exhibiting a wineglass-shaped black area, or without a wineglass-shaped black area. The tergite bands medianly interrupted; wide; incorporating complex figures. The spiracles of the third abdominal segment borne at or near the anterior corner of each side. The pale abdominal markings opaque, or somewhat translucent.
Larvae and pupae. The larvae abruptly tapering posteriorly; tailed. The anal segment abruptly constricted basally into the long, narrow tail; at least as long as the rest of the body (rat-tailed, with three pairs of fleshy projections before the anal opening). The larvae scarcely flattened; dark brown, plain; without thoracic hooks; mouth without triangular sclerites; anal segments with lappets. The larvae aquatic (rat-tailed maggots); saprophagous, or coprophagous (associated with wet decaying vegetation in mud in ponds, etc., also in farmyard manure and silage).
Classification. Subfamily Milesiinae; tribe Eristalini.
British representation. 5 species in Britain.
Illustrations. • H. pendulus, female (with Syrphus, Helophilus and Xanthogramma). • H. hybridus and H. pendulus: Verrall. • 15 genera (from Walker). • Eristalis fumipennis, Leucozona lucorum, Parhelophilus frutetorum, Spilomyia femorata: Stephens 1846. • H. transfugus L. (= ?), 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’.