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.
Ensifera is a suborder of insects that includes the various types of crickets and their allies including: true crickets, camel crickets, bush crickets or katydids, grigs, weta and Cooloola monsters. This and the suborder Caelifera make up the order Orthoptera. Ensifera is believed to be a more ancient group than Caelifera, with its origins in the Carboniferous period, the split having occurred at the end of the Permian period. Unlike the Caelifera, the Ensifera contain numerous members that are partially carnivorous, feeding on other insects, as well as plants.
The most recent understanding of the evolution of insects is based on studies of the following branches of science: molecular biology, insect morphology, paleontology, insect taxonomy, evolution, embryology, bioinformatics and scientific computing. It is estimated that the class of insects originated on Earth about 480 million years ago, in the Ordovician, at about the same time terrestrial plants appeared. Insects are thought to have evolved from a group of crustaceans. The first insects were landbound, but about 400 million years ago in the Devonian period one lineage of insects evolved flight, the first animals to do so. The oldest insect fossil has been proposed to be Rhyniognatha hirsti, estimated to be 400 million years old, but the insect identity of the fossil has been contested. Global climate conditions changed several times during the history of Earth, and along with it the diversity of insects. The Pterygotes underwent a major radiation in the Carboniferous while the Endopterygota underwent another major radiation in the Permian.
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.
Insect wings are adult outgrowths of the insect exoskeleton that enable insects to fly. They are found on the second and third thoracic segments, and the two pairs are often referred to as the forewings and hindwings, respectively, though a few insects lack hindwings, even rudiments. The wings are strengthened by a number of longitudinal veins, which often have cross-connections that form closed "cells" in the membrane. The patterns resulting from the fusion and cross-connection of the wing veins are often diagnostic for different evolutionary lineages and can be used for identification to the family or even genus level in many orders of insects.
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.
Bittacidae is a family of scorpionflies commonly called hangingflies or hanging scorpionflies.
The Panorpidae are a family of scorpionflies containing more than 480 species. The family is the largest family in Mecoptera, covering approximately 70% species of the order. Species range between 9–25 mm long.
The Choristidae are a small family of scorpionflies known only from Australia. Their larvae are found in moss mats.
Permotanyderus is an extinct genus of protodipteran insect of the Permotanyderidae family, first described by Edgar F. Riek in Australia in 1953 and which contains a single species P. ableptus.
Permotipula is an extinct monotypic genus of protodipteran insect which contains a single species Permotipula patricia. The only specimen of Permotipula was found in Late Permian strata of the Newcastle Coal Measures between the towns of Belmont and Warners Bay on the eastern side of Lake Macquarie, New South Wales, Australia and named by Robert J. Tillyard in 1929. The specimen consisting of a single well preserved wing, was considered lost after the death of Tillyard in 1937. The loss of the specimen and the mention by Tillyard of a second insect fossil from the same site, later described as Robinjohnia tillyardi resulted in much confusion regarding the taxonomic affiliations of P. patricia. Robinjohnia, a four winged insect which is now placed in the order Mecoptera. The P. patricia type specimen was found in the Tillyard collection which is housed at the British Museum and reexamined by R. Willmann in a 1989 paper. A second species, P. borealis was named by O.M. Martynova in 1961 from a small wing specimen found in the Kuznetsk Basin, Russia. This species was moved, however, in 1989 by R. Willmann to the monotypic genus Permila and is now considered a probable early mecopteran.
Titanoptera is an extinct order of neopteran insects from late Carboniferous to Triassic periods. Titanopterans were very large in comparison with modern insects, some having wingspans of up to 36 centimetres (14 in) or even 40 centimetres (16 in).
Dinopanorpidae is a small family of extinct insects in the order Mecoptera (scorpionflies) that contains two genera and seven species.
Palaeontinidae, commonly known as giant cicadas, is an extinct family of cicadomorphs. They existed from the Late Triassic to the Early Cretaceous. The family contains around 30 to 40 genera and around a hundred species.
Mesochorista proavita is an extinct species of scorpionfly from the Triassic period of Queensland, Australia.
Holcorpa is a genus of extinct insects in the scorpionfly order Mecoptera. Two Eocene age species found in Western North America were placed into the genus, H. dillhoffi and H. maculosa.
Austropanorpa is an extinct genus of scorpionfly. It is the only member of the family Austropanorpidae. The type species, A. australis was described by Edgar Riek in 1952 based on two incomplete forewings from the Redbank Plains Formation of Queensland, of probable Eocene age, and was assigned to Panorpidae. Later, it was recognised as distinctive enough to be assigned to its own monotypic family by Rainer Willman in 1977. In 2018 the species "Orthophlebia" martynovae from the Early Jurassic (Toarcian) aged Cheremkhovo Formation near Lake Baikal in Siberia, described by Irina Sukacheva in 1985, was recognised as belonging to the genus. The genus is distinguished from other mecopterans by having nine branched radial sectors and four veins in the medial sector of both wings, as opposed to living panorpoids which are typically 5 and rarely 6 branched.
Geinitziidae is an extinct family of polyneopteran insects, known from the Permian to Cretaceous. They are currently considered to be members "Grylloblattida" a poorly defined group of extinct insects thought to be related to modern ice crawlers (Grylloblattidae). Other authors place them in the extinct order Reculida. Unlike modern ice crawlers, which are wingless, they had large wings, bearing a superficial resemblance to cockroaches, and are thought to have been day-active above ground predators.
