| | Insects of Britain and Ireland: the genera of Syrphidae (hoverflies) |
Adult flies. The flies sphecid wasp-like (? - the female having been likened to Crossocerus quadrimaculatus), or cimbicid sawfly-like (a better match for the the narrow-bodied male); black or blackish, with pale marks; small; 7–9 mm long. Wings 4.25–7 mm long.
The head about the same width as the thorax. The face flat or concave in the region between the antennae and the mouth (concave); without a central knob; longitudinally keeled. The eyes bare. Antennae relatively short, drooping; with their bases well separated; black and ferruginous. The third antennal segment ovoid or orbicular. The antennal bristle dorsal; simple (bare).
The humeri hairy, and readily visible behind the head. The thorax pubescent without stiff bristles interspersed; patterned; with longitudinal stripes. The thoracic striping lateral only (greyish or silvery lateral or lateral-anterior stripes only). The scutellum flat, with a well defined edge; black. Wings plain (colourless); without a conspicuously dark stigma; divergent 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 to crossing it at or beyond the middle of the adjoining discal cell (near the middle). Vein R4+5 without a conspicuous curve projecting into the cell R5; without a backwardly projecting, incomplete transverse veinlet. The lower outer marginal vein markedly diverging from the posterior wing margin. The upper and lower outer marginal cross veins strongly stepped. The upper outer marginal cross-vein gently curved; joining vein R4+5 almost at right angles, so that cell R5 is not extended towards the wing tip; re-entrant to not re-entrant. The alula distinct to indistinct.
The abdomen narrower than the thorax; cylindric,almost linear, or more or less fusiform, or oblong (somewhat waisted in males); contrastingly patterned. The tergite patterning involving 2 and 3, or 2 to 4. The colour-patterned tergites marked with yellow to tawny, or silvery or greyish. The tergite bands medianly interrupted; narrow to wide.
Larvae and pupae. The larvae tapering posteriorly; shortly tailed. The anal segment tapered gradually to the spiracular process. The larvae scarcely flattened (sub-cylindrical, to about 12 mm long); darkish brown, plain; without thoracic hooks; mouth without triangular sclerites; anal segments with lappets. The larvae semi-aquatic to non-aquatic; saprophagous and coprophagous (short-tailed maggots, found in rotting compost, manure, silage, and decaying vegetation, but not under water).
Classification. Subfamily Milesiinae; tribe Xylotini.
British representation. 1 species in Britain (S. pipiens). Throughout the British Isles.
Illustrations. • S. pipiens: Verrall. • 15 genera (from Walker). 1, Ceriana conopsoides (adventive?), head in side view and extremity of wing. 2, Callicera aurata, with detail of antenna. 3, Microdon mutabilis, antenna and wing. 4, Eumerus strigatus, head in side view and wing. 5, Eristalis tenax: male head from above (5a), female head from the side (5b), and wing of female (5c). 6, Helophilus pendulus: head of male from above (6a) and from the side (6b), and extremity of wing (6c). 7, Merodon clavipes (extinct in Britain): head in side view, and hind leg of male. 8, Tropidia scita, male: head and extremity of wing. 9, Syritta pipiens, male, with head in side view (9a). 10, Xylota sylvarum, male: head (10a), antenna (10b), and base of hind leg showing coxa with a small spine (10d). 11, "Milesia speciosa" (Caliprobola speciosa?): head in side view (11a), wing extremity (11b), and base of hind leg (11c). 12, Criorhina berberina, with side view of head. 13, Volucella bombylans: side view of head (13a), antenna (13b), and wing extremity (13c). 14, Sericomyia silentis, with head from side (14a) and claw joint of tarsus (14b). 15, Orthoneura nobilis. From Walker (1851, Plate IX), with approximate lengths (head to abdominal tip) indicated. • S. pipiens, with assorted other Syrphidae (adult forms). Syrphidae. 1, Baccha elongata, female; 2, Neoascia podagrica, male; 3 and 4, Melanostoma scalare, male and female respectively; 5, Syritta pipiens, male; 6, Tropidia scita, male; 7 and 8, Sphaerophoria scripta, male and female respectively; 9, Sericomyia silentis, male; 10, Xylota segnis, male; 11, Rhingia camprestris, female; 12, Eupeodes luniger, male; 13, Episyrphus balteatus, female; 14, Helophilus transfugus L., female (= ?); 15, Chrysotoxum cautum, male; 16, Eristalis arbustorum, male. Adapted from C.O. Hammond, with names updated (Colyer and Hammond, 1968).
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’.
