British Insects: the Families of Diptera


L. Watson and M. J. Dallwitz



Adult insects. Very small to small; robustly-built. Antennae 3 segmented (the third rounded); ‘modified’; aristate (and the second segment sometimes with a downwardly curving spine); the arista dorsal (bare, or plumed only on its upper side). The second antennal segment not grooved. Ptilinal suture clearly defined. Ocelli present; 3. Eyes rounded, well separated. Post-vertical orbital bristles absent. Mouthparts functional. The maxillary palps 1 segmented; porrect. Vibrissae present (but poorly developed and not distict from the other bristles around the mouth), or absent. Thorax without a continuous dorsal suture; without well defined posterior calli. Wing venation incomplete, in the sense of lacking one or more of the cells. Wings without a discal cell (i.e., confluent with the 2nd basal cell); without a sub-apical cell; without a closed anal cell. The costa with two breaks (near the humeral cross vein, and near the end of vein 1). Sub-costa apparent, or absent or only dubiously identifiable (weakly developed except basally); joining vein 1 well short of the costa (weakly developed, and confused distally with vein 1). Wing vein 4 extending far beyond the end of the first basal cell. Wing vein 6 present; falling short of the wing margin. Wing vein 7 absent; reaching the wing margin, or falling short of the wing margin. Wings with the lower calypter much reduced or absent; patterned (e.g., Ilythea), or unpatterned. Tibiae without a dorsal pre-apical bristle. Hind tibiae without strong bristles in the basal 4/5. Predatory (on other insects), or neither parasitic nor predatory (feeding on decaying matter or excrement).

Larvae and pupae. The larvae aquatic (mainly), or terrestrial; phytophagous (within stems and shoots, often of water plants), or saprophagous, or coprophagous, or predatory; acephalic. The pupae enclosed within a puparium.

Comments. Very small to small flies of very damp places, some coastal. Wings sometimes with dark markings.

Classification. Suborder Brachycera; Division Muscomorpha Schizophora Acalyptratae; Superfamily Ephydroidea.

British representation. 142 species in Britain. Genera about 40; Athyroglossa, Allotrichoma, Atissa, Axysta, Clanoneurum, Coenia, Diclasiopa, Discocerina, Discomyza, Ditrichophora, Ephydra, Eutaenionotum, Gymnoclasiopa, Haloscatella, Hecamede, Hecamedoides, Hyadina, Hydrellia, Ilythea, Lamproscatella, Limnellia, Nostima, Notophila, Ochthera, Paracoenia, Parydra, Parydroptera, Pelina, Philotelma, iPhilygria, Polytrichophora, Psilopa, Scatella, Scatophila, Schema, Setacera, Teichomyza, Trimerina.

Illustrations. • Discocerina, Notiphila, Ochthera: Walker. • Ephydra, Hydrellia, Teichomyza: Walker. • Ilythea spilota Haliday in Curtis (Spotted-winged Ephydra: B. Ent. 413). • Ilythea spilota (detail: B. Ent. 413). • Ilythea spilota (dissections: B. Ent. 413). • Ilythea spilota (B. Ent. 413, legend+text). • Ilythea spilota (B. Ent. 413, text cont.).

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.’.