Flies are insects of the order Diptera, the name being derived from the Greek δι- di- "two", and πτερόν pteron "wing". Insects of this order use only a single pair of wings to fly, the hindwings having evolved into advanced mechanosensory organs known as halteres, which act as high-speed sensors of rotational movement and allow dipterans to perform advanced aerobatics. Diptera is a large order containing an estimated 1,000,000 species including horse-flies, crane flies, hoverflies, mosquitoes and others, although only about 125,000 species have been described.
Tipulidae is a family of large crane flies in the order Diptera. There are more than 30 genera and 4,200 described species in Tipulidae, common and widespread throughout the world.
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 Bibionomorpha are an infraorder of the suborder Nematocera. One of its constituent families, the Anisopodidae, is the presumed sister taxon to the entire suborder Brachycera. Several of the remaining families in the infraorder are former subfamilies of the Mycetophilidae, which has been recently subdivided. The family Axymyiidae has recently been removed from the Bibionomorpha to its own infraorder Axymyiomorpha.
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 Blephariceridae, commonly known as net-winged midges, are a nematoceran family in the order Diptera. The adults resemble crane flies except with a projecting anal angle in the wings, and different head shape, absence of the V on the mesonotum, and more laterally outstretched, forward-facing legs. They are uncommon, but dozens of genera occur worldwide, and over 200 species.
Chaoboridae, commonly known as phantom midges or glassworms, is a family of fairly common midges with a cosmopolitan distribution. They are closely related to the Corethrellidae and Chironomidae; the adults are differentiated through peculiarities in wing venation.
The Ptychopteridae, phantom crane flies, are a small family of nematocerous Diptera. Superficially similar in appearance to other "tipuloid" families, they lack the ocelli of the Trichoceridae, the five-branched radial vein of the Tanyderidae, and the two anal veins that reach the wing margins of the Tipulidae. They are usually allied with the Tanyderidae based on similarities of the mesonotal suture, this group being called the Ptychopteromorpha.
Mycetophilidae is a family of small flies, forming the bulk of those species known as fungus gnats. About 3000 described species are placed in 150 genera, but the true number of species is undoubtedly much higher. They are generally found in the damp habitats favoured by their host fungi and sometimes form dense swarms.
Limoniidae is the largest of four crane fly families, with more than 10,700 species in more than 150 genera. Some studies have suggested it to be a paraphyletic group, with some limoniids being more closely related to Tipulidae and Cylindrotomidae than to other limoniids. Limoniid crane flies can usually be distinguished by the way the wings are held at rest. Limoniids usually hold/fold the wings along the back of the body, whereas other crane flies usually hold them out at right angles. Snow flies such as Chionea scita have no wings at all. Limoniids are also usually smaller than other crane flies, with some exceptions.
The Perissommatidae are a family of flies (Diptera) that was proposed in 1962 by Donald Colless based on the species Perissomma fusca from Australia. The family now includes five extant species within the single genus Perissomma, four from Australia and one from Chile. The Perissommatidae are unusual as they appear to have four compound eyes. They have a small slender body less than 2 mm in length. Their wings are large in comparison to their bodies and subsequently their flight is weak. Preferring high-altitude forest environments, adults only fly in the winter. The larvae live in decaying leaf litter in wet sclerophyll or cool rain forests. Some species are suspected to be associated with fungi. In the case of Perissomma macalpinei, numbers of adults have been observed congregating in clumps of foliage and rising in short, zigzag flights in the sunlight above the foliage for short periods before descending.
Sciaroidea is a superfamily in the infraorder Bibionomorpha. There are about 16 families and more than 15,000 described species in Sciaroidea. Most of its constituent families are various gnats.
The Cylindrotomidae or long-bodied craneflies are a family of crane flies. More than 65 extant species in 9 genera occur worldwide. There are more than 20 extinct species.
Bolitophila is the sole living genus in the Bolitophilidae, a family of Diptera in the superfamily Sciaroidea, with around 40 Palaearctic and about 20 Nearctic species, and three species from the Oriental region (Taiwan). They are small (6–9 mm).
A gnat is any of many species of tiny flying insects in the dipterid suborder Nematocera, especially those in the families Mycetophilidae, Anisopodidae and Sciaridae. Most often they fly in large numbers, called clouds. "Gnat" is a loose descriptive category rather than a phylogenetic or other technical term, so there is no scientific consensus on what constitutes a gnat. Some entomologists consider only non-biting flies to be gnats. Certain universities and institutes also distinguish eye gnats: the Smithsonian Institution describes them as "non-biting flies, no bigger than a few grains of salt, ... attracted to fluids secreted by your eyes".
Anthracinae is a subfamily of bee flies in the family Bombyliidae. There are more than 80 genera and 2,000 described species in Anthracinae.
Lygistorrhininae, commonly called long-beaked fungus gnats is a subfamily of flies in the Diptera family Keroplatidae. The groups was long treated as a separate family, but molecular phylogenetic analysis has shown it to belong to Keroplatidae. There are about 7 genera and at least 30 described species in Lygistorrhininae.
Pygophora is a genus of flies belonging to the family Muscidae, comprising roughly 80 species as of 2023.
Limoniinae is a subfamily of limoniid crane flies in the family Limoniidae. There are more than 30 genera and 3,700 described species in Limoniinae, found worldwide.
