Belongs within: Schizophora.
The Sphaeroceridae are a family of small to minute flies often found on animal dung or other organic matter. They can usually be readily distinguished from other flies by the appearance of the first segment of the hind tarsus, which is distinctly swollen and/or shorter than the following segments (Colless & McAlpine 1991). This feature is less easily discerned in the Homalomitrinae, a Neotropical group of species that may be associated with army ants, in which all tarsal segments have become shortened. Members of the genus Homalomitra have the antennal scapes enlarged and almost contiguous medially (Marshall & Buck 2010).
Members of the subfamily Sphaerocerinae have the bristles on the scutellum reduced or replaced by spines, teeth or warts, and have a prominent lower face. The subfamilies Copromyzinae and Limosininae are less clearly distinguished but Copromyzinae often have the ocellar bristles inserted in front of the anterior ocellus and two pairs of orbital bristles. Limosininae have the ocellar bristles inserted between the ocelli and/or one pair of or no orbital bristles. The Argentinian genus Tucma has a single pair of orbital bristles, four scutellar bristles with the laterobasal pair small and hairlike, and a virtually bare arista (Marshall & Buck 2010).
Sphaerocerids are of little direct economic importance to humans though their abundance and ubiquity worldwide suggests they may play a major role in decomposition. Pullimosina heteroneura is commonly found in food-processing plants, and this and other species may become a nuisance in mushroom culture (Marshall & Richards 1987).
A little bit on lesser dung flies
Published 31 December 2013
The fly in the picture above is a typical member of the Sphaeroceridae, a family of over 1300 species of small flies that include some of the most ubiquitous of all insects. Despite their abundance, however, they rarely attract much attention from humans due to their small size, usually only about a couple of millimetres in length. Sphaerocerids are distinguished from other flies by the structure of the tarsus (the ‘foot’) on the hind leg. In most other flies, all the legs have the tarsi divided into elongate segments, but in sphaerocerids the first segment of the last tarsus is noticeably short and broad.
Sphaerocerids are sometimes referred to as ‘lesser dung flies’, referring of course to their small size and the diet of their larvae. However, lesser dung flies are not only associated with dung, but also feed on almost any form of decaying organic matter. They may be found on carrion or decaying vegetation or fungi. Some species may feed on a wide range of foodstuffs, but others are much pickier. One species, seemingly as yet unidentified, has been found in the excretory glands of a land crab. The coast-dwelling genus Thoracochaeta feeds on seaweed (Marshall & Buck 2010).
Though diverse, the majority of sphaerocerids are fairly conservative in appearance, including the Copromyza at the top of this post. There are, of course, notable exceptions. The individual just above is a representative of the Homalomitrinae, a rarely-collected subfamily of six known species in three genera from tropical Central and South America. The homalomitrines have a number of unusual features: their heads lack ocelli, have reduced bristles, and are more or less elongate; their thoraxes are relatively small; and the tarsi of all legs are short and broad. Two of the three genera, Sphaeromitra and Podiomitra, have markedly reduced venation in the wings. They do not have the appearance of strong fliers (though specimens have been collected in Malaise traps, indicating that they fly at least on occasion), but their extreme rarity (so far as is known) means that their lifestyles are almost unknown. Two species of Homalomitra, H. ecitonis and H. albuquerquei have been collected in association with army ants (Roháček & Marshall 1998), and it has been suggested that homalomitrines might develop in army ant middens, travelling phoretically by clinging to the ants with their modified tarsi (Marshall & Roháček 2003). However, it should be noted that this is largely speculative: the holotype of H. ecitonis, when collected, was reported to be walking amongst the supposed host ants, but otherwise little has been recorded of the nature of the association. It should also be noted that Roháček & Marshall (1998) suggested that H. ecitonis and H. albuquerquei form a clade to the exclusion of the other homalomitrine species, which further weakens confidence in extending the habits of these species to others.
There are also a number of species of sphaerocerid in which the wings are reduced or absent. The development of the wings may vary within a single species, as rather dramatically demonstrated by the specimen of Pullimosina meijerei shown above in a figure from Roháček (2012). This male exhibited unequal wing development, with the left wing that of a brachypterous individual but the right wing that of a macropter.
Sphaerocerids have been suspected as potential disease vectors due to their association with waste and decay, but actual evidence of negative impact on humans is rare. There appears to be at least one recorded case of sphaerocerid-caused intestinal myiasis (Marshall & Richards 1987), and sphaerocerids may become numerous enough to be a nuisance in places with a concentration of potential food, such as abattoirs or mushroom farms. Whatever their negative impacts may be, they are almost certainly outweighed by the positive: the ubiquitous sphaerocerids are probably major players in the process of breaking down waste materials and returning nutrients to the environment. They’re the little flies that save you from being knee-deep in shit.
Systematics of Sphaeroceridae
Characters (from Marshall & Buck 2010): Generally small acalyptrate flies (body length 0.7–6 mm, usually 1–3 mm). Body colour black to brown, rarely brightly patterned. Head with zero to (usually) one or two pairs of lateroclinate orbital bristles, interfrontal bristles usually distinct, vibrissae present but sometimes small, postocellar bristles (if present) convergent. Anepisternum bare or setulose, anepimeron usually bare (more rarely setulose), katepisternum with zero to three (usually one or two) dorsal bristles. Wing with two costal breaks, reduced subcosta, usually with cells bm and dm fused and an open cell cup. Wing occasionally patterned, reduced or lost. Mid tibia usually with sever (at least two) bristles. First, occasionally also second, hind tarsomere shortened and/or thickened.
<==Sphaeroceridae [Borboridae]
| i. s.: CarolinapteraM81
| Limomyza veniaMB10
| MonteithianaCM74
| BentrovataCM74
| AnatalantaRD77
|--Tucma [Tucminae]MB10
|--HomalomitrinaeMB10
| |--Homalomitra antiquaMB10
| |--Sphaeromitra ineptaMB10
| `--Podiomitra ostracotarsataMB10
|--BorborinaeK01
| |--Heteroptera acutangulaK01
| `--BorborusK01
| |--B. equinusK01
| |--B. oeneus Macquart 1847E12
| `--B. vitripennisK01
|--SphaerocerinaeMB10
| |--Sphaerocera curvipesMR87
| |--NeosphaeroceraMB10
| |--Mesosphaerocera annulicornisMB10
| |--ParasphaeroceraMB10
| `--IschioleptaMB10
| |--I. hyalophoraMB10
| |--I. ischnocnemisMB10
| |--I. micropygaMR87
| |--I. pusillaMB10 [=Sphaerocera (Ischiolepta) pusillaM83]
| `--I. scabriculaMB10
|--CopromyzinaeMB10
| |--PycnopotaMB10
| |--Lotophila atraMB10, MR87 [=Olinea atraMR87]
| |--PalaeoceropteraMB10
| |--PenolaMB10
| |--FrutillariaMB10
| |--AntropsMB10
| |--Copromyza equinaMB10
| |--Crumomyia [incl. Fungobia]MR87
| | `--C. annulusMR87
| |--ArchiborborusMB10
| | |--A. hirtipesMB10
| | `--A. orbitalisMB10
| |--BorborillusMR87
| | |--B. arcticaMR87
| | `--B. marginatis [=Copromyza (Borborillus) marginatis]M83
| `--NorrbomiaMB10
| |--N. gravisC07
| |--N. marginatisC07
| `--N. sordidaMB10
`--LimosininaeMB10
|--ArchiceropteraMB10
|--Archileptocera luteaMB10
|--BithecaMB10
|--Phthitia antillensisMB10
|--Sclerocoelus caribensisMB10
|--PseudocollinellaMB10
|--Rachispoda limosa [=Leptocera (Rachispoda) limosa]MB10
|--Anomioptera quinquealbaMB10
|--PalaeolimosinaMB10
|--PalaeocoprinaMB10
|--HellerellaMB10
|--Chespiritos sindecimusMB10
|--BromeloeciaMB10
|--Chaetopodella tonsaMB10
|--ArchicollinellaMB10
|--ElachisomaMB10
|--TrachyopellaMB10
|--GonioneuraMB10
|--ParasclerocoelusMB10
|--AptilotellaMB10
|--MyrmolimosinaMB10
|--RudolfinaMB10
|--Kimosina plumosula [=Limosina plumosula]MR87
|--Halidayina spinipennisMR87
|--ApteromyiaMR87
|--NearcticorpusMR87
|--PuncticorpusMR87
|--RudolfiaMR87
|--Ceroptera sivinskiiMR87
|--XenolimosinaMR87
|--Terrilimosina schmitzi [=Limosina schmitzi]MR87
|--PoecilosomellaMB10
| |--P. angulataMB10
| `--P. pectiniterga (Deeming 1964)JG19
|--TelomerinaMB10
| |--T. flavipesMB10
| `--T. minutissima [=Limosina minutissima]MR87
|--OpalimosinaMB10
| |--O. appendicula [=Limosina appendicula]MR87
| `--O. mirabilisMB10
|--AptilotusMB10
| |--A. parvipennisMR87
| `--A. spatulatusMR87
|--DruciatusMB10
| |--D. angustusMB10
| `--D. ovisternusMB10
|--PterogrammaMB10
| |--P. aquatileMB10
| `--P. pallicepsMB10
|--RobustagrammaMB10
| |--R. disjunctumMB10
| `--R. flavistylumMB10
|--CoproicaMB10
| |--C. ferruginataMB10
| `--C. hirtula [=Leptocera (Coproica) hirtula]M83
|--GyretriaMB10
| |--G. bisetaMB10
| `--G. melanogasterMB10
|--SpinilimosinaMB10
| |--S. brevicostataMB10
| `--S. rufifronsMB10
|--PullimosinaMB10
| |--P. heteroneura [=Limosina heteroneura]MR87
| |--P. pullulaMR87
| `--P. zayensisMB10
|--OpacifronsMB10
| |--O. coxata [=Leptocera (Opacifrons) coxata]MR87
| |--O. humidaWT11
| `--O. quartaMB10
|--LepidosinaMB10
| |--L. angusticercusMB10
| |--L. evanescensMB10
| `--L. inaequalisMB10
|--MinilimosinaMB10
| | i. s.: M. fungicola [=Limosina fungicola]MR87
| | M. zedaMR87
| |--M. (Allolimosina) rotundipennisMB10
| `--M. (Amputella) bistylusMB10
|--ThoracochaetaMB10
| |--T. brachystomaMB10
| |--T. johnsoniMR87
| |--T. seticostaMR87
| `--T. zosteraeMR87 [=Leptocera (Thoracochaeta) zosteraeT81]
|--SpelobiaMB10
| |--S. aciculataMB10
| |--S. (Bifronsina) bifronsMB10
| |--S. clunipesMR87
| |--S. (Spelobia) crassimana [=Limosina crassimana]MR87
| |--S. maculipennisMR87
| `--S. (Eulimosina) ochripesMR87
|--LeptoceraMB10
| | i. s.: L. caenosaMB10
| | L. fulvaBW09
| |--L. (Leptocera) fontinalisMR87
| `--L. (Pteremis)MR87
| |--L. (P.) nivalisMR87
| `--L. (P.) wirthiMR87
`--LimosinaK01
|--L. empirica [=Leptocera (Limosina) empirica]M83
|--L. limosa [=Borborus limosus]L49
|--L. mediospinosa [=Leptocera (Limosina) mediospinosa]M83
|--L. mirabilis [=Leptocera (Limosina) mirabilis]M83
|--L. pullula [=Leptocera (Limosina) pullula]M83
|--L. sacraR13
`--L. thomasi [=Leptocera (Limosina) thomasi]M83
*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.
[C07] Camerik, A. M. 2007. Ecological studies on phoretic females of dung-inhabiting Pediculaster (Acari: Heterostigmata, Pygmephoridae) species in South Africa: emigration patterns from cow and horse dung. In: Morales-Malacara, J. B., V. M. Behan-Pelletier, E. Ueckermann, T. M. Pérez, E. G. Estrada-Venegas & M. Badii (eds) Acarology XI: Proceedings of the International Congress pp. 649–655. Instituto de Biología and Faculdad de Ciencias, Universidad Nacional Autónoma de México, Sociedad Latinoamericana de Acarología: México.
[CM74] Colless, D. H., & D. K. McAlpine. 1974. Diptera (flies). In: CSIRO. The Insects of Australia: A textbook for students and research workers. Supplement 1974 pp. 91–96. Melbourne University Press.
[E12] Evenhuis, N. L. 2012. Publication and dating of the Exploration Scientifique de l’Algérie: Histoire Naturelle des Animaux Articulés (1846–1849) by Pierre Hippolyte Lucas. Zootaxa 3448: 1–61.
[JG19] James, D. J., P. T. Green, W. F. Humphreys & J. C. Z. Woinarski. 2019. Endemic species of Christmas Island, Indian Ocean. Records of the Western Australian Museum 34 (2): 55–114.
[K01] Kertész, K. 1901. Legyek [Dipteren]. In: Horváth, G. (ed.) Zichy Jenő Gróf Harmadik Ázsiai Utazása [Dritte Asiatische Forschungsreise des Grafen Eugen Zichy] vol. 2. Zichy Jenő Gróf Harmadik Ázsiai Utazásának Állattani Eredményei [Zoologische Ergebnisse der Dritten Asiatischen Forschungsreise des Grafen Eugen Zichy] pp. 179–201. Victor Hornyánszky: Budapest, and Karl W. Hierseman: Leipzig.
[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.
[M83] Martin, N. A. 1983. Miscellaneous observations on a pasture fauna: an annotated species list. DSIR Entomology Division Report 3: 1–98.
[MB10] Marshall, S. A., & M. Buck. 2010. Sphaeroceridae (small 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. 1165–1187. NRC Research Press: Ottawa.
[MR87] Marshall, S. A., & O. W. Richards. 1987. Sphaeroceridae. In: McAlpine, J. F. (ed.) Manual of Nearctic Diptera vol. 2 pp. 993–1006. Research Branch, Agriculture Canada.
Marshall, S. A., & J. Roháček. 2003. Podiomitra, a new genus of Homalomitrinae (Diptera: Sphaeroceridae) from Costa Rica. Proceedings of the Entomological Society of Washington 105 (3): 708–714.
[M81] McAlpine, J. F. 1981. Key to families—adults. In: McAlpine, J. F., B. V. Peterson, G. E. Shewell, H. J. Teskey, J. R. Vockeroth & D. S. Wood (eds) Manual of Nearctic Diptera vol. 1 pp. 89–124. Research Branch, Agriculture Canada.
[R13] Reuter, O. M. 1913. Lebensgewohnheiten und Instinkte der Insekten bis zum Erwachen der sozialen Instinkte. R. Friedländer & Sohn: Berlin.
[RD77] Richards, O. W., & R. G. Davies. 1977. Imms’ General Textbook of Entomology 10th ed. vol. 2. Classification and Biology. Chapman and Hall: London.
Roháček, J. 2012. Wing polymorphism in European species of Sphaeroceridae (Diptera). Acta Entomologica Musei Nationalis Pragae 52 (2): 535–558.
Roháček, J., & S. A. Marshall. 1998. Revision of Homalomitrinae subfam. n. (Diptera: Sphaeroceridae), with the description of a new genus and three new species. European Journal of Entomology 95: 455–491.
[T81] Teskey, H. J. 1981. Key to families—larvae. In: McAlpine, J. F., B. V. Peterson, G. E. Shewell, H. J. Teskey, J. R. Vockeroth & D. S. Wood (eds) Manual of Nearctic Diptera vol. 1 pp. 125–147. Research Branch, Agriculture Canada.
[WT11] Wiegmann, B. M., M. D. Trautwein, I. S. Winkler, N. B. Barr, J.-W. Kim, C. Lambkin, M. A. Bertone, B. K. Cassel, K. M. Bayless, A. M. Heimberg, B. M. Wheeler, K. J. Peterson, T. Pape, B. J. Sinclair, J. H. Skevington, V. Blagoderov, J. Caravas, S. N. Kutty, U. Schmidt-Ott, G. E. Kampmeier, F. C. Thompson, D. A. Grimaldi, A. T. Beckenbach, G. W. Courtney, M. Friedrich, R. Meier & D. K. Yeates. 2011. Episodic radiations in the fly tree of life. Proceedings of the National Academy of Sciences of the USA 108 (14): 5690–5695.