Acroceridae

Superregnum: Eukaryota
Regnum: Animalia
Subregnum: Eumetazoa
Cladus: Bilateria
Cladus: Nephrozoa
Cladus: Protostomia
Cladus: Ecdysozoa
Cladus: Panarthropoda
Phylum: Arthropoda
Subphylum: Hexapoda
Classis: Insecta
Cladus: Dicondylia
Subclassis: Pterygota
Cladus: Metapterygota
Infraclassis: Neoptera
Cladus: Eumetabola
Cladus: Endopterygota
Superordo: Panorpida
Cladus: Antliophora
Ordo: Diptera
Subordo: Brachycera
Infraordo: Asilomorpha
Superfamilia: Nemestrinoidea

Familia: Acroceridae
Subfamiliae (5 + 1†): Acrocerinae – Cyrtinae – Ogcodinae – Panopinae – Philopotinae – †Archocyrtinae
[Source: Gillung & Winterton (2019)]

Overview of genera (50 + 10†)

Acrocera – Africaterphis – Apelleia – Apsona – Archipialea – Asopsebius – Astomella – Astomelloides – Camposella – Carvalhoa – Coquena – Corononcodes – Cyrtus – Dimacrocolus – Eulonchus – Exetasis – Hadrogaster – Helle – Holops – Lasia – Lasioides – Leucopsina – Megalybus – Meruia – Mesophysa – Neophilopota – Nipponcyrtus – Ocnaea – Ogcodes – Oligoneura – Opsebius – Panops – Paracyrtus – Parahelle – Philopota – Physegastrella – Pialea – Psilodera – Pterodontia – Pteropexus – Quasi – Rhysogaster – Sabroskya – Schlingeriella – Stenopialea – Subcyrtus – Terphis – Thyllis – Turbopsebius – Villalus – †Archaeterphis – †Archocyrtus – ?†Burmacyrtus – †Cyrtinella – †Eulonchiella – †Glaesoncodes – †Hoffeinsomyia – †Prophilopota – †Schlingeromyia – †Villalites
Name

Acroceridae Leach, 1815
Synonyms

Cyrtidae Newman, 1834
Oncodidae Rondani, 1841: Kertész, 1909: 1

References
Primary references

Kertész, K. 1909. Catalogus dipterorum hucusque descriptorum. Volumen IV. Oncodidae, Nemestrinidae, Mydaidae, Apioceridae, Asilidae. G. Engelmann, Budapestini [=Budepest], 349 pp. BHL.
Leach, W.E. 1815. Entomology [pp. 57–172]. In: Brewster, D. (Ed). Brewster’s Edinburgh Encyclopedia. Volume IX [part I]. W. Blackwood, J. Waugh, etc., Edinburgh, 764 pp. BHL Reference page.

Additional references

Gillung, J.P. 2016. FAMILY ACROCERIDAE. In: Wolff, M.I., Nihei, S.S. & Carvalho, C.J.B. de (eds.), Catalogue of Diptera of Colombia. Zootaxa 4122(1): 346–349. DOI: 10.11646/zootaxa.4122.1.28 Paywall. PDF. Reference page.
Gillung, J.P. & Carvalho, C.J.B., de 2009. Acroceridae (Diptera): a pictorial key and diagnosis of the Brazilian genera. Zootaxa 2175: 29–41. Abstract & excerpt. DOI: 10.11646/zootaxa.2175.1.3 Paywall. PDF. Reference page.
Gillung, J.P. & Winterton, S.L. 2011. New genera of philopotine spider flies (Diptera, Acroceridae) with a key to living and fossil genera. ZooKeys 127: 15–27. DOI: 10.3897/zookeys.127.1824 Open access. Reference page.
Gillung, J.P. & Winterton, S.L. 2017. A review of fossil spider flies (Diptera: Acroceridae) with descriptions of new genera and species from Baltic Amber. Journal of Systematic Palaeontology 16(4): 325–350. DOI: 10.1080/14772019.2017.1289566 Paywall. ResearchGate Open access. Reference page.
Gillung, J.P. & Winterton, S.L. 2019. Evolution of fossil and living spider flies based on morphological and molecular data (Diptera, Acroceridae). Systematic Entomology 44(4): 820–841. DOI: 10.1111/syen.12358 Open access. Reference page.
González, C.R., Elgueta, M. & Ramírez, F. 2018. A catalog of Acroceridae (Diptera) from Chile. Zootaxa 4374(3): 427–440. DOI: 10.11646/zootaxa.4374.3.6 Paywall. ResearchGate Open access. Reference page.
Hauser, M. & Winterton, S.L. 2007. A new fossil genus of small-headed flies (Diptera: Acroceridae: Philopotinae) from Baltic amber. Annals of the Entomological Society of America 100(2): 152–156. DOI: 10.1603/0013-8746(2007)100[152:ANFGOS]2.0.CO;2 Paywall. PDF. Reference page.
Kehlmaier, C. & Almeida, J.M. 2014. New host records for European Acroceridae (Diptera), with discussion of species limits of Acrocera orbiculus (Fabricius) based on DNA-barcoding. Zootaxa 3780(1): 135–152. DOI: 10.11646/zootaxa.3780.1.5 Paywall. Reference page.
Kerr, P.H. & Winterton, S.L. 2008. Do parasitic flies attack mites? Evidence in Baltic amber. Biological journal of the Linnean Society 93(1): 9–13. DOI: 10.1111/j.1095-8312.2007.00935.x
Larrivée, M. & Borkent, C.J. 2009. New spider host associations for three acrocerid fly species (Diptera, Acroceridae). Journal of arachnology 37(2): 241–242. DOI: 10.1636/T08-62.1
Nartshuk, E.P. 1996. A new fossil acrocerid fly from the Jurassic beds of Kazakhstan (Diptera: Acroceridae). Zoosystematica rossica 4(2): 313–315.
Paramonov, S.J. 1955. New Zealand Cyrtidae (Diptera) and the problem of the Pacific Island fauna. Pacific science 9(1): 16–25. hdl: 10125/8835 Open access
Paramonov, S.J. 1957. A review of Australian Acroceridae (Diptera). Australian journal of zoology 5(4): 521–546. DOI: 10.1071/ZO9570521
Schlinger, E.I. 1960. A review of the South African Acroceridae (Diptera). Annals of the Natal Museum 14(3): 459–504. BioNames.
Winterton, S.L., Wiegmann, B.M. & Schlinger, E.I. 2007. Phylogeny and Bayesian divergence time estimations of small-headed flies (Diptera: Acroceridae) using multiple molecular markers. Molecular phylogenetics and evolution 43(3): 808–832. DOI: 10.1016/j.ympev.2006.08.015

Links

Australasian/Oceanian Diptera Catalog -- Web Version
Catalogue of Life: 2011 Annual Checklist

Vernacular names
Deutsch: Kugelfliegen
English: small-headed flies
日本語: コガシラアブ科
Türkçe: Balon böceğigiller
中文: 小头虻科

The Acroceridae are a small family of odd-looking flies. They have a hump-backed appearance with a strikingly small head, generally with a long proboscis for accessing nectar. They are rare and not widely known. The most frequently applied common names are small-headed flies or hunch-back flies.[2] Many are bee or wasp mimics. Because they are parasitoids of spiders, they also are sometimes known as spider flies.

Description
Acroceridae plate from Johann Wilhelm Meigen's Europäischen Zweiflügeligen

The Acroceridae vary in size from small to fairly large, about the size of large bees, with a wingspan over 25 mm in some species. As a rule, both sexes have tiny heads and a characteristic hump-backed appearance because of the large, rounded thorax.

In appearance, they are compact flies without major bristles, but many species have a bee-like hairiness on their bodies, and some are bee or wasp mimics. In most species, the eyes are holoptic in both sexes, the heads seemingly composed mainly of the large faceted eyes. This is in contrast to many insects in which the males have larger (even holoptic) eyes, whereas the females have normal eyes. The squamae are disproportionately large, completely covering the halteres, and the abdomen has an inflated appearance, often practically globular.[3] The tarsi are equipped with large claws with three pulvilli below them.
Taxonomy

The Acroceridae are a small family in the Brachycera. They are members of the infraorder Muscomorpha, and DNA studies suggest that they are most closely related to the families Nemestrinidae and Bombyliidae.[4] A 2013 analysis of morphological data suggested the Acroceridae were a sister group to the Asiloidea and Eremoneura.[5]

The roughly 520 species are placed in 50 genera. In 2019, a revised classification of the family based on phylogenetic studies was published, listing five extant subfamilies and one extinct subfamily containing Archocyrtus from the Late Jurassic Karabastau Formation of Kazakhstan.[1]

Obsolete synonyms for Acroceridae include Cyrtidae, Oncodidae, and Ogcodidae.
Distribution and habitat

Acroceridae are cosmopolitan in distribution, but nowhere abundant. They appear episodically and in most places are rarely observed; of more than 500 species described, most are known from fewer than 10 specimens. They occur most commonly in semiarid tropical locations.
Eulonchus sapphirinus feeding on Clintonia uniflora
Behaviour

As far as is known, all Acroceridae are parasitoids of spiders. They are most commonly collected when a spider from the field is brought into captivity. As in the related families, Bombyliidae and Nemestrinidae, members of the family undergo hypermetamorphosis: the adults do not seek out their hosts; instead, the first-instar larva is a planidium. Females lay large number of eggs, up to 5,000, and after hatching, the planidia seek out spiders. They do not resemble the triungulin of most beetles with a hypermetamorphosis, but do resemble the triungulin of Stylops. The larva can move with a looping movement like a leech or inchworm, and can leap several millimetres into the air. When a spider contacts an acrocerid planidium, the planidium grabs hold, crawls up the spider's legs to its body, and forces its way through the body wall, usually at an articulation membrane. Often, it lodges near a book lung,[3] where it may remain for years before completing its development. Mature larvae pupate outside the host.
Psilodera species, showing the proboscis below the body, holoptic eyes, texture of wings, and bee mimicry

The adults of most species, like various members of the Tabanidae, Nemestrinidae, and Bombyliidae, are nectar feeders with exceptionally long probosces, sometimes longer than the entire body length of the insect. Unlike the other families, however, when not deploying the proboscis for feeding, the Acroceridae carry it lengthwise medially beneath the body, instead of projecting forward. As a result, the proboscis might escape casual notice, though careful inspection may reveal it projecting slightly behind the abdomen.

Flies are usually found in small numbers on plants in July and August in the Palearctic realm.
References

Gillung, Jessica P.; Winterton, Shawn L. (2019). "Evolution of fossil and living spider flies based on morphological and molecular data (Diptera, Acroceridae)". Systematic Entomology. 44 (4): 820–841. doi:10.1111/syen.12358.
Gillung, Jéssica P.; Winterton, Shaun L. (2011). "New genera of philopotine spider flies (Diptera, Acroceridae) with a key to living and fossil genera". ZooKeys (127): 15–27. doi:10.3897/zookeys.127.1824. PMC 3175128. PMID 21998545.
Richards, O. W.; Davies, R.G. (1977). Imms' General Textbook of Entomology: Volume 1: Structure, Physiology and Development Volume 2: Classification and Biology. Berlin: Springer. ISBN 0-412-61390-5.
Wiegmann, Brian M; Yeates, David K; Thorne, Jeffrey L; Kishino, Hirohisa. Time Flies, a New Molecular Time-Scale for Brachyceran Fly Evolution Without a Clock. Syst. Biol. 52(6):745–756, 2003. ISSN 1063-5157 print / ISSN 1076-836X. Online doi:10.1080/10635150390250965

Lambkin, Christine L., et al. "The phylogenetic relationships among infraorders and superfamilies of Diptera based on morphological evidence." Systematic Entomology 38.1 (2013): 164-179.