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 more than 150,000 species including horse-flies, crane flies, hoverflies, mosquitoes and others.
Pterygota is a subclass of insects that includes all winged insects and groups who lost them secondarily.
Neoptera is a classification group that includes most orders of the winged insects, specifically those that can flex their wings over their abdomens. This is in contrast with the more basal orders of winged insects, which are unable to flex their wings in this way.
The Culicomorpha are an infraorder of Nematocera, including mosquitoes, black flies, and several extant and extinct families of insects. They originated 176 million years ago, in the Triassic period. There are phylogenetic patterns that are used to interpret bionomic features such as differences in the nature of blood-feeding by adult females, daytime or nighttime feeding by adult females, and occurrence of immature stages in aquatic habitats.
Oestroidea is a superfamily of Calyptratae including the blow flies, bot flies, flesh flies, and their relatives. It occurs worldwide and has about 15,000 described species.
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.
Holometabola, also known as Endopterygota, is a supra-ordinal clade of insects within the infraclass Neoptera that go through distinctive larval, pupal, and adult stages. They undergo a radical metamorphosis, with the larval and adult stages differing considerably in their structure and behaviour. This is called holometabolism, or complete metamorphism.
Megaloptera is an order of insects. It contains the alderflies, dobsonflies and fishflies, and there are about 300 known species.
Mecoptera is an order of insects in the superorder Holometabola with about six hundred species in nine families worldwide. Mecopterans are sometimes called scorpionflies after their largest family, Panorpidae, in which the males have enlarged genitals raised over the body that look similar to the stingers of scorpions, and long beaklike rostra. The Bittacidae, or hangingflies, are another prominent family and are known for their elaborate mating rituals, in which females choose mates based on the quality of gift prey offered to them by the males. A smaller group is the snow scorpionflies, family Boreidae, adults of which are sometimes seen walking on snowfields. In contrast, the majority of species in the order inhabit moist environments in tropical locations.
Holometabolism, also called complete metamorphosis, is a form of insect development which includes four life stages: egg, larva, pupa, and imago. Holometabolism is a synapomorphic trait of all insects in the superorder Holometabola. Immature stages of holometabolous insects are very different from the mature stage. In some species the holometabolous life cycle prevents larvae from competing with adults because they inhabit different ecological niches. The morphology and behavior of each stage are adapted for different activities. For example, larval traits maximize feeding, growth, and development, while adult traits enable dispersal, mating, and egg laying. Some species of holometabolous insects protect and feed their offspring. Other insect developmental strategies include ametabolism and hemimetabolism.
The Exopterygota, also known as Hemimetabola, are a superorder of insects of the subclass Pterygota in the infraclass Neoptera, in which the young resemble adults but have externally developing wings. They undergo a modest change between immature and adult, without going through a pupal stage. The nymphs develop gradually into adults through a process of moulting.
Nannochoristidae is a family of scorpionflies with many unusual traits. It is a tiny, relict family with a single extant genus, Nannochorista, with eight species occurring in New Zealand, southeastern Australia, Tasmania, Argentina and Chile. Due to the group's distinctiveness from other scorpionflies, it is sometimes placed in its own order, the Nannomecoptera. Some studies have placed them as the closest living relatives of fleas. Most mecopteran larvae are eruciform, or shaped like caterpillars. Nannochoristid larvae, however, are elateriform, and have elongated and slender bodies. The larvae are aquatic, which is unique among mecopterans. The larvae are predatory, hunting on the beds of shallow streams, primarily on the larvae of aquatic Diptera like chironomids. The adults are thought probably to be adapted to liquid feeding, likely on flower nectar and/or the juice of fruits. Adults of Australian and South American species are often found in habitats like the edges of streams, lakes, as well as montane bogs. Australian species have been observed visiting the foliage and flowers of Leptospermum.
Boreidae, commonly called snow scorpionflies, or in the British Isles, snow fleas are a very small family of scorpionflies, containing only around 30 species, all of which are boreal or high-altitude species in the Northern Hemisphere.
Empididae is a family of flies with over 3,000 described species occurring worldwide in all the biogeographic realms but the majority are found in the Holarctic. They are mainly predatory flies like most of their relatives in the Empidoidea, and exhibit a wide range of forms but are generally small to medium-sized, non-metallic and rather bristly.
Amphiesmenoptera is an insect superorder, established by S. G. Kiriakoff, but often credited to Willi Hennig in his revision of insect taxonomy for two sister orders: Lepidoptera and Trichoptera (caddisflies). In 2017, a third fossil order was added to the group, the Tarachoptera.
The Neuropterida are a clade, sometimes placed at superorder level, of holometabolous insects with over 5,700 described species, containing the orders Neuroptera, Megaloptera, and Raphidioptera (snakeflies).
Paraneoptera or Acercaria is a superorder of insects which includes lice, thrips, and hemipterans, the true bugs. It also includes the extinct order Permopsocida, known from fossils dating from the Early Permian to the mid-Cretaceous.
Apystomyia is a genus of flies in the family Apystomyiidae. The genus contains the single living Apystomyiidae species, Apystomyia elinguis, which is primarily found in California. Details of its life history are largely unknown. The extinct genus Hilarimorphites is known from the Cretaceous Burmese and New Jersey ambers. Formerly placed in the Asiloidea, molecular phylogenetic studies in 2010 placed the genus unambiguously as a sister of the Cyclorrhapha within the clade Eremoneura.
Panorpida or Mecopterida is a proposed superorder of Holometabola. The conjectured monophyly of the Panorpida is historically based on morphological evidence, namely the reduction or loss of the ovipositor and several internal characteristics, including a muscle connecting a pleuron and the first axillary sclerite at the base of the wing, various features of the larval maxilla and labium, and basal fusion of CuP and A1 veins in the hind wings. The monophyly of the Panorpida is supported by recent molecular data.
Eremoneura is a clade of flies within the Brachycera that includes the Empidoidea and the Cyclorrhapha and is a sister of the Asilomorpha. They are thought to have evolved around the Mesozoic. The group includes fossils described in the genus Chimeromyia from 125 million year old amber which show both empidoid and cyclorrhaphan characters. The monotypic family Apystomyiidae has also been placed within the Eremoneura as a sister of the Cyclorrhapha.
