Insects of Britain and Ireland: the genera of Syrphidae (hoverflies)
Adult flies. The flies megachilid bee-like (E. strigatus and E. tuberculatus, cf. Osmia caerulescens, Hoplitis claviventris and Stelis ornatula), or sphecid wasp-like (E. sabulonum, cf. Gorytes tumidus and Nysson dimidiatus); blackish or dark bronze with silvery spots on the tergites, or reddish with a blackish thorax; minute to medium sized; 5–11.5 mm long. Wings 3.25–6.75 mm long.
The head somewhat wider than the thorax to about the same width as the thorax. The face without a central knob; neither keeled nor impressed. The eyes depicted as bare. Antennae relatively short, drooping; with their bases approximated (seated on a tubercle); black, or red, or ferruginous. The antennal bristle dorsal; shorter than the third segment to much longer than the third segment; simple.
The humeri hairy, and readily visible behind the head. The thorax pubescent to glabrous?; indistinctly patterned, or plain; with longitudinal stripes (these faint, greyish, in E. strigatus), or without longitudinal stripes. The scutellum somewhat convex, with undefined edge (E. strigatus), or flat, with a well defined edge; variously at least partly yellow (yellow towards the hind border, in E. ornatus), or aeneous, or brownish, ferrugineous or tawny, or black. Wings plain (colourless to grey, sometimes tawny along the fore border); with a conspicuous dark stigma (often, this brown or tawny), or without a conspicuously dark stigma; divergent in repose, or 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. 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 conspicuously bent near the base the base and conspicuously bent well above the base (being twice-angled, in E. strigatus); re-entrant. The alula distinct.
The abdomen about the same width as the thorax to narrower than the thorax; oval, or oblong, or obovate, or more or less fusiform; with 6 segments apparent. The male abdomen with 4 visible segments. The abdomen not conspicuously furry; contrastingly patterned (segments 2–4 reddish to tawny in E. sabulonum), or not contrastingly patterned. The tergite patterning involving 2 to 4. The colour-patterned tergites marked with whitish (in E. strigatus), or silvery or greyish, or tawny to orange. The tergite bands medianly interrupted, or partially interrupted and entire; narrow, or 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 tapering anteriorly and posteriorly from the middle; posteriorly blunt and tail-less; flattened (prolegs absent); pale brown, plain; without thoracic hooks; mouth without triangular sclerites; anal segments with lappets (the middle pair on the anal segment divided into two small projections). The larvae phytophagous; feeding on Alliaceae, Amaryllidaceae, Iridaceae, and Umbelliferae (mostly known from cultivated monocot bulbs or rhizomes, but E. tubeculatus has also been recorded from parsnip).
Classification. Subfamily Milesiinae; tribe Merodontini.
British representation. 4 species in Britain.
Illustrations. • Eumerus sabulonum: B. Ent. 749. • Eumerus sabulonum: B. Ent. 749, legend+text. • Eumerus sabulonum: B. Ent. 749, text cont.. • Eumerus ornatus: Verrall. • E. ornatus, E. sabulonum and E. strigatus: Verrall. • 15 genera (from Walker).
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’.