The Nymphomyiidae are a family of tiny (2 mm) slender, delicate flies (Diptera). Larvae are found among aquatic mosses in small, rapid streams in northern regions of the world, including northeastern North America, Japan, the Himalayas, and eastern Russia. Around a dozen extant species are known, with two fossil species found in amber, extending back to the Mid Cretaceous. Under an alternative classification, they are considered the only living representatives of a separate, suborder called Archidiptera which includes several Triassic fossil members. The family has characteristics associated with the Nematocera as well as the Brachycera. The antennae are shortened as in the Brachycera and these flies are long, having a snout with vestigeal mouthparts, non-differentiated abdominal segments with large cerci. The wings are narrow and hair-fringed and have very weak venation. They are known to form cloud-like swarms in summer and the short-lived non-feeding adults have wings that fracture at the base shortly after mating.
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. Many are bee or wasp mimics. Because they are parasitoids of spiders, they also are sometimes known as spider flies.
The Nematoceran family Axymyiidae is the sole member of the infraorder Axymyiomorpha, though it is often included within the infraorder Bibionomorpha in older classifications. It is known from only nine species in four genera, plus eight fossil species.
Nemestrinidae, or tangle-veined flies is a family of flies in the superfamily Nemestrinoidea, closely related to Acroceridae. The family is small but distributed worldwide, with about 300 species in 34 genera. Larvae are endoparasitoids of either grasshoppers (Trichopsideinae) or scarab beetles (Hirmoneurinae). Some are considered important in the control of grasshopper populations. Adults are often observed on flowers.
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.
Neophilopota is a genus of small-headed flies. It contains only a single species, Neophilopota brevirostris, described by Schlinger in 2013. It is endemic to Mexico.
Acrocera is a genus of small-headed flies in the family Acroceridae.
Ogcodes is a cosmopolitan genus of small-headed flies in the family Acroceridae. About 90 species have been described for the genus. It is the most common and speciose genus in its family. These flies are endoparasitoids of ground-dwelling entelegyne spiders.
Acrocera melanderi is a species of small-headed flies in the family Acroceridae.
Acrocera obsoleta is a species of small-headed flies in the family Acroceridae.
Pterodontia is a genus of small-headed flies. There are at least 20 described species in Pterodontia.
Ocnaea is a genus of small-headed flies. There are 20 described species in Ocnaea.
Lasia is a genus of small-headed flies in the family Acroceridae. There are about 19 described species in Lasia, which are distributed in the New World.
Corononcodes is a genus of small-headed flies. It is known from South Africa and the Palearctic realm.
Exetasis is a genus of small-headed flies. It is known from Brazil and Argentina.
Arrhynchus is a genus of small-headed flies in the family Acroceridae. It was formerly considered a synonym of Ocnaea, but was reinstated as a valid genus by Schlinger in 1968. It is endemic to Chile.
Ulidiini is a tribe of picture-winged flies in the family Ulidiidae that live in the arid and sub arid regions of the Palaearctic. There are three genera and around 100 species within the tribe. The tribe was first named in 1835; its type genus is Ulidia.
Psilodera fasciata, also known as the banded humpback fly, is a species of small-headed fly found in South Africa. It is the most common species in its genus.
