Belongs within: Schizophora.
The Milichiidae are a group of small flies that are mostly saprophages or coprophages though a number of species are associated with social Hymenoptera as inquilines or kleptoparasites. Members of several genera have been found in assocation with large spiders and feeding on partially digested prey (Swann 2010). Members are divided between the subfamilies Madizinae, with a prominent vibrissal angle, the vibrissa below the lower margin of the eye, and without a prominent anal area on the wing, and the Milichiinae, with the vibrissal angle scarcely evident and the vibrissa above the level of the lower margin of the eye, and a conspicuously broad anal area on the wing (Sabrosky 1987).
Freeloading flies
Published 15 November 2019
The world is home to an awful lot of small flies. Enough, in fact, that they are divided by those who study them between a large number of families, though many are difficult to distinguish without close examination. Among the more ubiquitous of these small fly families are the Milichiidae.
Milichiid flies may be found around the world though they often escape attention due to their small size (seven millimetres is at the upper end of their range). The greater number of species are dark in coloration, with a smaller number yellow or orange. They may generally be distinguished from other flies by wing venation, with two distinct breaks along the costal vein on the front margin of the wing, where it is joined by the humeral and subcostal veins, and with a small closed posterior cubital (cup) cell near the back of the base of the wing. The bristle pattern on the head usually includes two or three pairs of medioclinate frontal bristles and two or three pairs of lateroclinate to proclinate orbital bristles, though notable exceptions exist (Swann 2010). Sexual dimorphism is rare in the family though males and females differ in frons width in some African species (Deeming 1981).
The habits of milichiids are poorly known. It is thought that the majority pursue the typical fly lifestyle of feeding and breeding on ordure such as decaying and faecal matter. However, more distinctive habits are characteristic of some exemplars. A number of milichiids act as kleptoparasites, sucking fluids from prey captured by spiders, assassin bugs and other predators. Some may have an even closer relationship with such hosts: orb-web spiders in Western Australia have been observed spreading their chelicerae to allow Desmometopa to feed around them, seemingly acting as cleaners. The same flies were also observed feeding around the spiders’ anus following defecation (Brake & von Tschirnhaus 2010). Larvae of several milichiid species have been recorded as inquilines in ant and bee nests (Swann 2010). Adults of Milichia species have also been recorded associating with ants, soliciting regurgitated food or licking anal secretions. The species M. patrizii has been recorded in South Africa chasing Crematogaster castanea ants and pinning them down, using the bases of the antennae to grasp the ant’s appendages (Wild & Brake 2009). The fly then induces the ant to regurgitate food, possibly using long setae on the proboscis to essentially ‘tickle its throat’. Such behaviours have lead to some authors bestowing milichiids with the name of “freeloader flies”. As yet, the flies seem unconcerned by this attack on their character.
Systematics of Milichiidae
Characters (from Swann 2010): Small (body length 1–7 mm), often largely brown or black, occasionally orange or yellow; males of some genera with silvery microtomentum on abdomen. Usually with two or three pairs of medioclinate frontal bristles and two or three pairs of lateroclinate to proclinate orbital bristles; rarely with uniform row of 8–10 pairs of reclinate fronto-orbital bristles or frontal and orbital setae greatly reduced to absent. Frons usually with two rows of interfrontal setae, sometimes on distinctly shining stripes; lunule often with one or two pairs of setae; proboscis often elongate, geniculate. Wing with humeral and subcostal break; region of latter often modified into costal lappet; cell cup closed, small. Male terminalia with pregonites fused with hypandrium and postgonites absent.
<==Milichiidae [Phyllomyzidae]S10 | i. s.: Costalima myrmicolaS10 | PseudomilichiaS10 | Ulia poecilogastraS10 | MicrosimusS10 | ProsaetomilichiaO98 | Pseudodesmometopa succineum Hennig 1971P92 |--MilichiinaeS10 | |--EusiphonaS87 | | |--E. miraS10 | | `--E. vittataS10 | |--MilichiellaS87 [incl. EccoptommaS10] | | |--M. bisignataS10 | | `--M. lacteipennisS10 | |--MilichiaS10 | | |--M. aethiopsS10 | | |--M. albomaculata (Strobl 1900)C-T92 | | |--M. piscivoraCM91 | | `--M. speciosa Meigen 1830C-T92 | `--PholeomyiaS87 | |--P. comansS87 | |--P. dampfiS10 | |--P. indecoraS87 | `--P. leucozonaS10 `--Madizinae [Phyllomyzinae]S10 |--Madiza glabra Fallén 1820C-T92 |--Paramyia nitensS87, S10 |--Aldrichiomyza agromyzinaS87, S10 |--StomosisS87 | |--S. innominataS10 | `--S. rufulaS10 |--LeptometopaS87 | |--L. halteralisS10 | `--L. latipes (Meigen 1830)C-T92 [=Desmometopa latipesS10] |--DesmometopaS87 | |--D. m-nigrum (Zetterstedt 1848)C-T92 | |--D. sordida (Fallén 1820)C-T92 | `--D. varipalpis Malloch 1927C-T92 |--PhyllomyzaS10 | |--P. hurdi Sabrosky 1963P92 | |--P. jaegeri Hennig 1967P92 | `--P. securicornisS10 `--Neophyllomyza Melander 1913S87, C-T92 |--N. acyglossa (Villeneuve 1920)C-T92 |--N. magnipalpusS10 |--N. quadricornisS10 `--N. wulpiS10
*Type species of generic name indicated
References
Brake, I., & M. von Tschirnhaus. 2010. Stomosis arachnophila sp. n., a new kleptoparasitic species of freeloader flies (Diptera, Milichiidae). ZooKeys 50: 91–96.
[C-T92] Carles-Tolrá, M. 1992. New and interesting records of Diptera Acalyptrata from Spain. Part I: Acartophthalmidae, Opomyzidae, Anthomyzidae, Asteiidae, Carnidae, Tethinidae, Milichiidae and Cryptochetidae. Bull. Annls Soc. R. Belge Ent. 128: 343–353.
[CM91] Colless, D. H., & D. K. McAlpine. 1991. Diptera (flies). In: CSIRO. The Insects of Australia: A textbook for students and research workers 2nd ed. vol. 2 pp. 717–786. Melbourne University Press: Carlton (Victoria).
Deeming, J. C. 1981. Some new African Milichiidae (Diptera: Cyclorrhapha) having pronounced sexual dimorphism of the frons. Zoological Journal of the Linnean Society 71: 159–169.
[O98] Oosterbroek, P. 1998. The Families of Diptera of the Malay Archipelago. Brill: Leiden.
[P92] Poinar, G. O., Jr. 1992. Life in Amber. Stanford University Press: Stanford.
[S87] Sabrosky, C. W. 1987. Milichiidae. In: McAlpine, J. F. (ed.) Manual of Nearctic Diptera vol. 2 pp. 903–908. Research Branch, Agriculture Canada.
[S10] Swann, J. E. 2010. Milichiidae (milichiid 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. 1125–1136. NRC Research Press: Ottawa.
Wild, A. L., & I. Brake. 2009. Field observations on Milichia patrizii ant-mugging flies (Diptera: Milichiidae: Milichiinae) in KwaZulu-Natal, South Africa. African Invertebrates 50 (1): 205–212.