Scathophagidae

Belongs within: Anthomyiidae.
Contains: Scathophaga.

The Scathophagidae are a group of slender, bristly flies that are predaceous on other insects as adults. Larvae are more varied in habits, including saprophagous, predatory and plant-feeding species (Vockeroth 2010).

To dung and beyond

Published 7 April 2021

When most people think of a fly, odds are that they imagine one of the group of flies known as calyptrates. This is the clade that includes, among others, such animals as house flies, blow flies and flesh flies. Calyptrates are often reasonably large as flies go and they often have life styles (such as larvae feeding on decaying matter) that bring them close to humans and their homes. One of the most recognisable features of this clade, and the inspiration for its name, is enlargement of the lower calypter, a lobe at the base of the wing. This lower calypter can be moved semi-independently of the rest of the wing which is how calyptrate flies are able to fly acrobatically and avoid being swatted. Nevertheless, there is one significant subgroup of ‘calyptrate’ flies that has foregone the advantages of an enlarged calypter, commonly recognised as the family Scathophagidae.

The Scathophagidae are a modestly diverse family of flies with about 250 known species, the great majority of which are found in the Holarctic region (Vockeroth 1987). Only a handful of species are found in more southerly regions, mostly at higher altitudes. They are medium-sized flies, ranging between three and eleven millimetres in length, fairly similar to a house fly in overall appearance but generally more slender and bristly. They are commonly referred to as ‘dung flies’, in reference to the larval diet of one of the most widespread and best known species, Scathophaga stercoraria (whose scientific name broadly and appropriately translates as ‘shit-eater, thing of shit’). However, despite the unremarkable number of species, scathophagids are actually more diverse in their larval habits. As far as we know, adult scathophagids are all predators on other insects.

Scathophagids are divided between two subfamilies, distinguished by features of the male terminalia. In Scathophaginae, the sixth abdominal tergite (dorsal plate) of the male is hairy and usually separate from the following fused syntergosternite 7 + 8 (with dorsal and ventral plates of the segments fused to form a ring). In Delininae, the sixth tergite lacks hairs and is always fused to the following syntergosternite. The subfamilies also differ in life history. Larvae of Delininae are leaf-miners on monocots, hatching from eggs laid on the leaf surface. The Scathophaginae are more diverse. As already indicated, some are saprobes. As well as the dung-feeding S. stercoraria, the genus Scathophaga also includes species which specialise on rotting seaweed on the sea-shore (a milieu which, offhand, supports a range of fly species belonging to numerous families). Other species are, like the Delininae, miners in plant tissue though they are found in a wider range of hosts (both monocots and dicots) and their eggs are inserted by the female directly into the plant tissue. A handful are aquatic or semi-aquatic predators, feeding on small invertebrates along lake shores or in sewage, or on the eggs of caddisflies in fast-running streams.

Considering the more derived character of the male terminalia in the Delininae, and the more disparate life habits of the Scathophaginae, some authors have suggested that the latter may be paraphyletic to the former. It has also been presumed that the Scathophagidae as a whole is ancestrally saprobic, considering that saprobic habits are also the norm in related fly families such as the Muscidae (house flies). However, a molecular phylogenetic analysis of the Scathophagidae by Kutty et al. (2007) supported monophyly of both subfamilies. Their results indicated that the original scathophagids were plant-feeders with saprobic lineages arising within the family on two separate occasions. Predatory larvae also evolved twice, once as a further development from saprobes and once direct from plant-feeding ancestors. The diet of this family started out fresh but, somewhere along the line, some species decided they’d rather eat muck.

Systematics of Scathophagidae

Characters (from Vockeroth 2010): Slender, medium-sized (body length 6.5–13 mm), strongly bristled and sometimes setose flies, subshining to densely pruinose. Wing clear or with crossveins clouded. Frons about as wide as head in both sexes, without cruciate interfrontal bristles. Arista nearly bare to plumose. Palpus slightly broadened toward apex. Anepisternum extensively bare on anteroventral portion or with abundant fine setae on anterior one-quarter; katepisternum with one strong bristle posterodorsally. Postmetacoxal bridge present or absent. Vein R₁ bare or setose above; A₁ reaching wing margin. Female abdomen with seven pairs of spiracles.

<==Scathophagidae [Cordiluridae, Scathophaginae]
    |--+--Norellia Robineau-Desvoidy 1830KP10, F92 [incl. Norellitoma Wahlgren 1917F92]
    |  |    |  i. s.: N. longiabdomina Sun 1991F92
    |  |    |         N. triangula Sun 1991F92
    |  |    |--+--N. spinipes (Meigen 1826)KP10, F92 [=Cordylura spinipesF92; incl. *N. pseudonarcissi Robineau-Desvoidy 1830F92]
    |  |    |  `--+--N. spinimanaKP10
    |  |    |     `--N. striolataKP10
    |  |    `--+--N. liturataKP10
    |  |       `--+--N. flavicorneKP10
    |  |          `--N. mirusaeKP10
    |  `--+--+--ScathophagaKP10
    |     |  `--+--AcerocnemaKP10
    |     |     |    |--A. macroceraKP10
    |     |     |    `--A. rufulaV87
    |     |     `--GimnomeraKP10
    |     |          |--G. cuneiventrisKP10
    |     |          |--G. tarseaKP10
    |     |          `--+--G. cereaKP10
    |     |             `--G. dorsataKP10
    |     `--+--+--Cleigastra apicalisKP10
    |        |  `--Neorthacheta dissimilisKP10, V87
    |        `--+--Orthacheta cornutaKP10
    |           `--Nanna Becker 1894KP10, F92 [incl. Amaurosoma Becker 1894F92]
    |                |  i. s.: N. katmaiensisV87
    |                |         N. truncata Fan 1976F92
    |                |--N. brunneicostaKP10
    |                `--+--N. tibiellaKP10
    |                   `--+--N. inermisKP10
    |                      `--+--N. fasciataKP10
    |                         `--+--*N. flavipes (Fallen 1819)F92, KP10, F92 [=Cordylura flavipesF92]
    |                            `--N. articulataKP10
    `--+--DelininaeKP10
       |    |--Chylizosoma vittatumKP10
       |    `--+--Americina adustaKP10, V87
       |       `--Delina nigritaKP10, V87
       `--CordiluraKP10
            |  i. s.: C. bisignataO98
            |         C. brevicornisV10
            |         C. exhumataV87
            |         C. flavicaudaL49
            |         C. vetustaV87
            |         C. (Cordilura)V87
            |           |--C. (C.) proboscideaV87
            |           `--C. (C.) rufipesV87
            |         C. (Acicephala) politaV87
            |         C. (Paratidia) criddleiV87
            |         C. (Scoliaphleps) ustulataV87
            |         C. (Snyderia) praeustaV87
            |--C. carbonariaKP10
            `--+--+--Phrosia albilabrisKP10
               |  `--C. pudicaKP10
               `--+--C. albipesKP10
                  |--C. atrataKP10
                  |--C. latifronsKP10
                  |--C. ontarioKP10
                  |--C. puberaKP10
                  |--C. (Achaetella) varipesV87, KP10
                  |--+--C. ciliataKP10
                  |  `--C. umbrosaKP10
                  `--+--C. dimidataKP10
                     `--C. (Cordilurina)V87
                          |--C. (C.) fuscipesV87
                          `--C. (C.) pleuricataV87, KP10

Scathophagidae incertae sedis:
  ScatogeraBW09
  Ernoneura argusV87
  AllomyellaV87
  Neochirosia atrifronsV87
  Pleurochaetella simplicipesV87
  StaegeriaV87
  Hexamitocera loxocerataV87
  Peratomyia vittataV87
  Plethochaeta varicolorV87
  Norellisoma spinimanumV87
  Cosmetopus longusV87
  MegaphthalmaV87
    |--M. longicornisO98
    `--M. pallidaV87
  Bucephalina (Neogimnomera) amansV87
  Brooksiella varicornisV87
  CordylurellaV87
  Huckettia nearcticaV87
  Megaphthalmoides unilineatusV87
  GonarcticusV87
  Gonatherus planicepsV87
  Parallelomma vittatumV87
  Synchysa tricinctaV87
  Dromogaster incomptaV87

*Type species of generic name indicated

References

[BW09] Buck, M., N. E. Woodley, A. Borkent, D. M. Wood, T. Pape, J. R. Vockeroth, V. Michelsen & S. A. Marshall. 2009. Key to Diptera families—adults. In: Brown, B. V., A. Borkent, J. M. Cumming, D. M. Wood, N. E. Woodley & M. A. Zumbado (eds) Manual of Central American Diptera vol. 1 pp. 95–156. NRC Research Press: Ottawa.

[F92] Fan Z. 1992. Key to the Common Flies of China 2^nd ed. Science Press: Beijing.

Kutty, S. N., M. V. Bernasconi, F. Šifner & R. Meier. 2007. Sensitivity analysis, molecular systematics and natural history evolution of Scathophagidae (Diptera: Cyclorrhapha: Calyptratae). Cladistics 23: 64–83.

[KP10] Kutty, S. N., T. Pape, B. M. Wiegmann & R. Meier. 2010. Molecular phylogeny of the Calyptratae (Diptera: Cyclorrhapha) with an emphasis on the superfamily Oestroidea and the position of Mystacinobiidae and McAlpine’s fly. Systematic Entomology 35: 614–635.

[L49] Lucas, H. 1849. Exploration Scientifique de l’Algérie pendant les années 1840, 1841, 1842 publiée par ordre du gouvernement et avec le concours d’une commission académique. Sciences physiques. Zoologie. II. Histoire naturelle des animaux articulés. Troisième partie. Insectes (suite). Imprimerie Nationale: Paris.

[O98] Oosterbroek, P. 1998. The Families of Diptera of the Malay Archipelago. Brill: Leiden.

[V87] Vockeroth, J. R. 1987. Scathophagidae. In: McAlpine, J. F. (ed.) Manual of Nearctic Diptera vol. 2 pp. 1085–1097. Research Branch, Agriculture Canada.

[V10] Vockeroth, J. R. 2010. Scathophagidae (dung flies). In: Brown, B. V., A. Borkent, J. M. Cumming, D. M. Wood, N. E. Woodley & M. A. Zumbado (eds) Manual of Central American Diptera vol. 2 pp. 1267–1269. NRC Research Press: Ottawa.