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| Insects of Britain and Ireland: the genera of Syrphidae (hoverflies) |
Adult flies. The flies black or blackish, sometimes patterned tawny to orange; small to medium sized; (6–)7–10(–11) mm long. Wings 4.5–9.25 mm long.
The head wider than the thorax to about the same width as the thorax. The face flat or concave in the region between the antennae and the mouth; without a central knob (covered with long, drooping shaggy hairs); not elongated horizontally into a cone as long as the rest of the head. The frons not inflated. The eyes hairy. Antennae relatively short, drooping; seated on a prominant part of the frons; black, or black and ferruginous. The third antennal segment ovoid or orbicular. The antennal bristle dorsal; shorter than the third segment to much longer than the third segment; simple (pubescent).
The humeri hairy, and readily visible behind the head. The thorax pubescent without stiff bristles interspersed; plain; without longitudinal stripes. The scutellum black. Wings patterned, or plain (sometimes darkened in the disc); with a conspicuous dark stigma, or without a conspicuously 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 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 slightly stepped to strongly stepped. The upper outer marginal cross-vein conspicuously bent near the base the base; strongly angled to vein R4+5, so that cell R5 is markedly extended towards the wing tip; not re-entrant. The alula distinct. The hypopleuron with no long hairs on its upper transverse ridge.
The abdomen wider than the thorax to about the same width as the thorax; flattened, narrowly obovate, or oval. The male abdomen with 4 visible segments. The abdomen with tergites 2, 3 and 4 all more or less well developed; not conspicuously furry; contrastingly patterned, or not contrastingly patterned. The tergite patterning involving (when present) 2 (only). The colour-patterned tergites marked with yellow to tawny. The tergite patterning when present, confined to tergite 2. The interrupted band on tergite 2 reduced to small paired spots, or not reduced to small spots. The tergite bands medianly interrupted (being represented by large spots on tergite 2); narrow to wide. The spiracles of the third abdominal segment borne at or near the anterior corner 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 to flattened (hemispherical); green, or not green; green or dark brown, patterned, or plain; dorsally smooth, without projections; mouth with a triangular sclerite on either side; anal segments without lappets. The larvae predatory (on a wide range of arboreal and ground-layer aphids).
Classification. Subfamily Milesiinae; tribe Pipizini.
British representation. 4 species in Britain.
Illustrations. • Pipiza noctiluca: Verrall. • 18 genera (from Walker). 1, Chrysotoxum cautum, male: head (1a) and abdomen (1b) from the side. 2, "Psarus abdominalis" (not British?), side view of head (2a), and antenna (2b). 3, Paragus haemorrhous, male: head from above (3a) and side (3b), and tip of wing (3c). 4, Psilota anthracina: head from side (4a), and wing (4b). 5a, Pipiza noctiluca: head from the side. 6a, Orthoneura elegans: antenna. 7a-b, Chrysogaster cemiteriorum: head from the side (7a), and wing tip (7b). 7c, "Chrysogaster nigricollis" (= ?), wing tip. 8, "Brachyopa conica" (not British?), with head in side view (8a). 9, Rhingia rostrata: male head from above (9a) and from the side (9b). 10, Ferdinandea cuprea, with (10a) details of labrum and lingua showing one maxilla and its palp. 11a, Cheilosia illustrata: male head from the side. 11b and 11c, Cheilosia leucorum: proboscis (11b) and wing tip (11c). 12, Scaeva pyrastri, female, and (12a) head of male. 13a, Doros profuges: 8-jointed female abdomen. 14, Sphaerophoria interrupta, male, with extremity of the abdomen (14a); 14b, Sphaerophoria interrupta, abdomen of female. 15a and 15b, Baccha elongata: abdomen and hind leg. 16, Sphegina clunipes. 17a and 17b, Neoascia podagrica: head from the side, and wing tip. [18, Physocephala rufipes (Conopidae), and details of head from the side (18a), proboscis (18b), and antenna (18c)]. From Walker (1851, Plate X), with approximate lengths (head to abdominal tip) indicated.
We advise against extracting comparative information from the descriptions. This is much more easily achieved using the DELTA data files or the interactive key, which allows access to the character list, illustrations, 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. See also Guidelines for using data taken from Web publications.
Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 2003 onwards. Insects of Britain and Ireland: the genera of Syrphidae (hoverflies). Version: 27th July 2019. delta-intkey.com’.
