British Insects: the Families of Diptera

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L. Watson and M. J. Dallwitz

Sepsidae

Life style non-parasitic.

Adult insects. Small; slender-bodied to robustly-built; not stilt-legged. The back of the head very convex. Antennae 2 segmented, or 3 segmented; ‘modified’; aristate; the arista dorsal (not plumed). The second antennal segment not grooved. Ptilinal suture clearly defined. Ocelli present; 3. Eyes rounded, well separated. Lower orbital bristles present, or absent; when present, curved forward. Post-vertical orbital bristles present; divergent. Mouthparts functional. The maxillary palps 1 segmented (vestigial); porrect. Vibrissae present, or absent. Thorax without a continuous dorsal suture; without well defined posterior calli. Wing venation complete, in the sense of exhibiting 1st and 2nd basal, anal and discal cells (usually), or incomplete, in the sense of lacking one or more of the cells (the basal part of vein 4 sometimes absent, so that the two basal cells are not separated). Wings with a discal cell; with a subapical cell (or this almost closed), or without a sub-apical cell; with a closed anal cell. The anal cell short. The costa unbroken. Sub-costa apparent; reaching the costa independently of vein 1. The leading edge veins not noticeably stronger than the rest. Wing vein 4 extending far beyond the end of the first basal cell. Wing vein 6 present; falling short of the wing margin (short and straight). Wing vein 7 absent. Wings with the lower calypter much reduced or absent; unpatterned (but sometimes with a dark apical spot). Tibiae with a dorsal pre-apical bristle (e.g., Sepsis punctum), or without a dorsal pre-apical bristle. Hind tibiae without strong bristles in the basal 4/5. Abdomen constricted basally (often, lending an ant-like appearance), or not constricted basally.

Larvae and pupae. The larvae terrestrial; saprophagous, or coprophagous (in mammal faeces and vertebrate carcasses); acephalic. The pupae enclosed within a puparium.

Comments. Small black or brownish flies, sometimes metallic and shining. The occiput very convex, Always with one or more bristles across the posterior spiracle, just below and in front of the haltere. The male forelegs often exhibit curiously deformed femora and tibiae armed with spines or thorny protuerances..

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

British representation. 27 species in Britain. Genera 6; Meroplius, Nemopoda, Orygma, Saltella, Sepsis, Themira.

Illustrations. • Nemopoda, Orygma, Saltella, Sepsis, Themira (from Walker). • Themira annulipes (Ring-footed Fly: B. Ent. 245). • Themira annulipes (detail, dissections: B. Ent. 245). • Themira annulipes: B. Ent. 245, legend+text. • Themira annulipes: B. Ent. 245, 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. http://delta-intkey.com’.

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