British Insects: the Families of Diptera


L. Watson and M. J. Dallwitz


Clegs, Horse-flies, Gad-flies, Stouts.

Life style parasitic (the females only), or non-parasitic (the males); on parasitic humans and mammals other than humans (the adult females including notorious blood-suckers of medical and veterinary significance).

Adult insects. Small to large. Antennae 3 segmented; ‘modified’ (the third segment annulated); having the terminal segment annulated; not aristate. Ocelli absent. Eyes asymmetric, nearly or quite connected above the antennae (males), or rounded, well separated (females). Mouthparts functional; stout, adapted for piercing (the blood-sucking females), or non-piercing (males). Mandibles present (in both males and females). Mandibles not in the form of long, slender, piercing stylets. The maxillary palps 1 segmented, or 2 segmented; porrect (males), or drooping (females). Vibrissae absent. Wing veins reaching the margin between the anal cell and the lower fork of vein 3 4. Wings with a discal cell; with a subapical cell (or the veins markedly converging distally), or without a sub-apical cell; with a closed anal cell. The anal cell relatively long. The costa extending around the entire wing. Sub-costa apparent; reaching the costa independently of vein 1. The leading edge veins not noticeably stronger than the rest. Wing vein 3 distally forked (the wide fork embracing the apex of the wing). The fork of wing vein 3 broad, its lower branch reaching the wing margin well below the apex. Wing vein 6 present; reaching the wing margin. Wing vein 7 present; falling short of the wing margin. Wings with a well developed lower calypter. Tibiae spurred. Feet with a triple pad beneath the tarsal claws. Parasitic (the females, which suck blood), or neither parasitic nor predatory (the males, which mostly subsist on plant exudates and secretions).

Larvae and pupae. The larvae terrestrial; predatory (on worms, insect larvae and crustaceans, in a variety of damp situations); hemicephalic. The pupae without a puparium.

Comments. Robust, more or less flattened, large-headed flies without bristles, mostly mottled brown, tawny or grey. Eyes large, often irridescent.

Classification. Suborder Brachycera; Division Tabanomorpha; Superfamily Tabanoidea.

British representation. 30 species in Britain. Genera 5; Atylotus, Chrysops, Haemotopota, Hybomitra, Tabanus.

Illustrations. • Chrysops, Haematopota, Tabanus (from Walker). • Atylotus fulvus (Alpine Breeze-fly or Clegg: B. Ent. 078). • Atylotus fulvus (detail: B. Ent. 078). • Atylotus fulvus (dissections: B. Ent. 078). • Atylotus fulvus (B. Ent. 078, legend+text). • Atylotus fulvus (text, cont.: B. Ent. 078). • Haematopota italica (= grandis? Mersey Island Clegg: B. Ent. 525). • Haematopota italica (= grandis? detail: B. Ent. 525). • Haematopota italica (= grandis? dissections: B. Ent. 525). • Haematopota italica (= grandis? B. Ent. 525, legend+text). • Haematopota italica (= grandis? text, cont.: B. Ent. 525).

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. British insects: the families of Diptera. Version: 1st January 2012.’.