Insects of Britain and Ireland: the genera of Syrphidae (hoverflies)
Adult flies. The flies vespid wasp-like (e.g., cf. P. frutetorum and Vespula rufa); piceous black, marked yellow to tawny; small to medium sized; about 8–11.5 mm long. Wings 7–9 mm long.
The head somewhat wider than the thorax to about the same width as the thorax. The face ground-coloured at least part yellow; flat or concave in the region between the antennae and the mouth to not flat or retreating between antennae and mouth; with a central knob to without a central knob; produced below and extending beyond the antennae, or not extending below beyond the antennae; with tubercles; elongated and tuberculated. The eyes bare. Antennae relatively short, drooping; with their bases approximated (seated on a tubercle); yellowish, or tawny. The third antennal segment ovoid or orbicular. The antennal bristle dorsal; much longer than the third segment; simple.
The humeri hairy, and readily visible behind the head. The thorax pubescent without stiff bristles interspersed; patterned; not exhibiting a skull-like figure; with longitudinal stripes (these yellowish). The scutellum somewhat convex, with undefined edge; brownish, ferrugineous or tawny (ferrugineous). Wings plain (slightly grey); with a conspicuous dark stigma; 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 at or beyond the middle of the adjoining discal cell (near the middle). 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 about the same width as the thorax to narrower than the thorax; obovate (to almost orbicular, sometimes straight-sided). The male abdomen with 4 visible segments. The abdomen not conspicuously furry; contrastingly patterned. The tergite patterning involving 2 and 3 (less conspicuous on 3). The colour-patterned tergites marked with yellow to tawny. The dorsum of tergite 2 exhibiting a wineglass-shaped black area. The tergite bands medianly interrupted (so as to result in complex dark figures); wide. The spiracles of the third abdominal segment borne at or near the anterior corner of each side. The pale abdominal markings opaque.
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). The larvae scarcely flattened (the prolegs with crochets in three or more rows); plain; without thoracic hooks; mouth without triangular sclerites; anal segments with lappets. The larvae aquatic; saprophagous, or phytophagous and saprophagous (? - recorded in Typha leaf sheaths); mostly in decaying vegetation (in ponds and slow-moving water).
General comments. Adults lacking the bare facial stripe of Helophilus.
Classification. Subfamily Milesiinae; tribe Eristalini.
British representation. 3 species in Britain.
Illustrations. • P. versicolor: Verrall. • Eristalis fumipennis, Leucozona lucorum, Parhelophilus frutetorum, Spilomyia femorata: Stephens 1846.
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’.