Small-headed flies Temporal range: | |
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Pterodontia sp. fly | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Arthropoda |
Class: | Insecta |
Superorder: | Panorpida |
(unranked): | Antliophora |
Order: | Diptera |
Suborder: | Brachycera |
Superfamily: | Nemestrinoidea |
Family: | Acroceridae Leach, 1815 |
Subfamilies [1] | |
Synonyms | |
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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. [3]
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. [4] The tarsi are equipped with large claws with three pulvilli below them.
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. [5] A 2013 analysis of morphological data suggested the Acroceridae were a sister group to the Asiloidea and Eremoneura. [6]
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.
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.
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, [4] where it may remain for years before completing its development. Mature larvae pupate outside the host.
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.
The Bombyliidae are a family of flies, commonly known as bee flies. Adults generally feed on nectar and pollen, some being important pollinators. Larvae are mostly parasitoids of other insects.
The Asiloidea comprise a very large superfamily insects in the order Diptera, the true flies. It has a cosmopolitan distribution, occurring worldwide. It includes the family Bombyliidae, the bee flies, which are parasitoids, and the Asilidae, the robber flies, which are predators of other insects.
A planidium is a specialized form of insect larva seen in the first-instar of a few families of insects that have parasitoidal ways of life. They are usually flattened, highly sclerotized (hardened), and quite mobile. The function of the planidial stage is to find a host on which the later larval instars may feed, generally until the insect pupates.
Nemestrinoidea is a small, monophyletic superfamily of flies, whose relationship to the other Brachycera is uncertain; they are sometimes grouped with the Tabanomorpha rather than the Asilomorpha. They are presently considered to be the sister taxon to the Asiloidea. The group contains two very small extant families, the Acroceridae and Nemestrinidae, both of which occur worldwide but contain only small numbers of rare species. One extinct family, Rhagionemestriidae, is also included in Nemestrinoidea.
Mythicomyiidae, commonly called mythicomyiids, are very tiny flies (0.5–5.0 mm) found throughout most parts of the world, especially desert and semi-desert regions, except the highest altitudes and latitudes. They are not as common in the tropics, but genera such as Cephalodromia and Platypygus are known from these regions. Many of these "microbombyliids" have a humpbacked thorax and lack the dense vestiture common in the Bombyliidae. Mythicomyiids have until recently not had much attention in the literature. Their small size has caused them to be missed when collecting. Yellow pan trapping and fine-mesh netting in Malaise and aerial sweep nets has resulted in a number of undescribed species from many parts of the world. A high diversity of both genera and species exists for this family in Africa, especially northern and southern portions. About 350 species are known. Hundreds more await description.
Bombylius major is a parasitic bee mimic fly. B. major is the most common type of fly within the Bombylius genus. The fly derives its name from its close resemblance to bumblebees and are often mistaken for them.
Acrocerinae is a subfamily of small-headed flies in the family Acroceridae. Their larvae are endoparasites of araneomorph spiders, with the exception of Carvalhoa appendiculata which can develop as ectoparasitoids on their host spiders. Traditionally, the subfamily included the genera now placed in Cyrtinae and Ogcodinae, but the subfamily in this sense was found to be polyphyletic and was split up in 2019.
Philopotinae is a subfamily of small-headed flies. They have an arched body shape, as well as enlarged postpronotal lobes that form a collar behind the head. Their larvae are endoparasites of araneomorph spiders in the subgroup Entelegynae.
Panopinae is a subfamily of small-headed flies (Acroceridae). Their larvae are endoparasites of spiders in the infraorder Mygalomorphae.
Apystomyiidae is a small family of flies containing the living genus Apystomyia and the extinct genera Apystomimus and Hilarimorphites. The single living Apystomyiidae species, Apystomyia elinguis, is native to California. Species of Hilarimorphites have been described from Mid to late Cretaceous Burmese and New Jersey ambers, while the single Apystomimus species is from the Late Jurassic of Kazakhstan.
Eulonchus halli is a species of small-headed flies in the family Acroceridae. It was named after one of its original collectors, Jack C. Hall, who was also a colleague of the species's author, Evert I. Schlinger, at the University of California.
Eulonchus is a genus of small-headed flies in the family Acroceridae. There are six described species in Eulonchus. The genus is found in North America. Adults have a metallic blue, green or sometimes purple coloration, giving them a jewel-like appearance. A common name for flies in the genus is the North American jewelled spider flies. Adults are also known as "sapphires" or "emeralds".
Eulonchus tristis is a species of small-headed flies in the family Acroceridae.
Archocyrtus is an extinct genus of small-headed flies in the family Acroceridae. The genus is known from compression fossils from the Late Jurassic Karabastau Formation of Kazakhstan. The genus is the only member of the subfamily Archocyrtinae.
Burmacyrtus is an extinct genus of small-headed flies of uncertain placement. The genus is known from Upper Cretaceous fossils in amber from Myanmar. It contains only one species, Burmacyrtus rusmithi.
Archaeterphis is an extinct genus of small-headed flies in the family Acroceridae. It is known from Baltic amber from the Eocene, though the locality is unknown. It contains only one species, Archaeterphis hennigi.
Sabroskya is a genus of small-headed flies in the family Acroceridae. It is known from South Africa and Malawi. It is named after the American entomologist Curtis Williams Sabrosky.
Ogcodes zonatus is a species of insect in the family Acroceridae, the small-headed flies.
Cyrtinae is a subfamily of the Acroceridae. Their larvae are endoparasites of araneomorph spiders in the subgroup Entelegynae.
Euchariomyia is a monotypic genus of the subfamily Bombyliinae. The only species is Euchariomyia dives.