The name Apterygota is sometimes applied to a subclass of small, agile insects, distinguished from other insects by their lack of wings in the present and in their evolutionary history; notable examples are the silverfish, the firebrat, and the jumping bristletails. Their first known occurrence in the fossil record is during the Devonian period, 417–354 million years ago.
Currently, no species are listed as being at conservation risk.
The term Apterygota refers to two separate clades of wingless insects: Archeognatha comprises jumping bristletails, while Zygentoma comprises silverfish and firebrats. The Zygentoma are in the clade Dicondylia with winged insects, a clade that includes all other insects. The group Apterygota is not a clade; it is paraphyletic.
Temporal range: Devonian–Present 
|Petrobius maritimus (Archaeognatha: Machilidae)|
The primary characteristic of the apterygotes is they are primitively wingless. While some other insects, such as fleas, also lack wings, they nonetheless descended from winged insects but have lost them during the course of evolution. By contrast, the apterygotes are a primitive group of insects that diverged from other ancient orders before wings evolved. Apterygotes, however, have the demonstrated capacity for directed, aerial gliding descent from heights. It has been suggested by researchers that this evolved gliding mechanism in apterygotes might have provided an evolutionary basis from which winged insects would later evolve the capability for powered flight.
Apterygotes also have a number of other primitive features not shared with other insects. Males deposit sperm packages, or spermatophores, rather than fertilizing the female internally. When hatched, the young closely resemble adults and do not undergo any significant metamorphosis, and lack even an identifiable nymphal stage. They continue to molt throughout life, undergoing multiple instars after reaching sexual maturity, whereas all other insects undergo only a single instar when sexually mature.
Apterygotes possess small appendages, referred to as "styli", on some of their abdominal segments, but play no part in locomotion. They also have long, paired abdominal cerci and a single median, tail-like caudal filament, or telson.
The composition and classification of Apterygota changed over time. By the mid-20th century, the subclass included four orders (Collembola, Protura, Diplura, and Thysanura). With the advent of a more rigorous cladistic methodology, the subclass was proven paraphyletic. While the first three groups formed a monophyletic group, the Entognatha, distinguished by having mouthparts submerged in a pocket formed by the lateral and ventral parts of the head capsule, the Thysanura (Zygentoma plus Archaeognatha) appeared to be more closely related to winged insects. The most notable synapomorphy proving the monophyly of Thysanura+Pterygota is the absence of intrinsic antennal muscles, which connect the antennomeres in entognaths, myriapods, and crustaceans. For this reason, the whole group is often termed the Amyocerata, meaning "lacking antennal muscles".
However, the Zygentoma are now considered more closely related to the Pterygota than to the Archaeognatha, thus rendering even the amyocerate apterygotes paraphyletic, and resulting in the dissolution of Thysanura into two separate monophyletic orders.
Aleksandr Grigorevich Sharov (А.Г. Шаров, 1922—1973) is a Russian palaeoentomologist, paleontologist and expert on Pterosauria. He graduated from Moscow State University. In 1951 he defended Candidate of Science dissertation on the embryology of Apterygota. Since 1951 he worked at the Paleontological Institute in Moscow, where in 1966 he defended dissertation of Doctor of Science. His major contribution to the phylogeny of Arthropods was published in 1966.
He worked during the 1960s and 1970s on the Karatau rocks and discovered many of the fossils, of which some have been named after him, as in the case of the Karatausuchus sharovi (a crocodile), and Sharovipteryx (a reptile related to pterosaurs). He also discovered and described the specimen Sordes pilosus in 1971 and Longisquama insignis.Amphiesmenoptera
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 (butterflies and moths) and Trichoptera (caddisflies). In 2017, a third fossil order was added to the group, the Tarachoptera.Trichoptera and Lepidoptera share a number of derived characters (synapomorphies) which demonstrate their common descent:
Females, rather than males, are heterogametic (i.e. their sex chromosomes differ).
Dense setae are present in the wings (modified into scales in Lepidoptera).
There is a particular venation pattern on the forewings (the double-looped anal veins).
Larvae have mouth structures and glands to make and manipulate silk.Thus these two extant orders are sisters, with Tarachoptera basal to both groups. Amphiesmenoptera probably evolved in the Jurassic. Lepidoptera differ from the Trichoptera in several features, including wing venation, form of the scales on the wings, loss of the cerci, loss of an ocellus, and changes to the legs.Amphiesmenoptera are thought to be the sister group of Antliophora, a proposed superorder comprising Diptera (flies), Siphonaptera (fleas) and Mecoptera (scorpionflies). Together, Amphiesmenoptera and Antliophora compose the group Mecopterida.Aptera
Aptera is an obsolete taxonomic category, which included the Apterygota along with various other wingless arthropods.
Aptera may also refer to:
Aptera (Greece), the city in Crete
Aptera (Lycia), an ancient city in Lycia, now Turkey
Aptera Motors, a defunct automobile company that was to produce the Aptera 2e
Aptera 2 Series, a concept car developed by the automobile company Aptera Motors
Aptera (genus), a genus of cockroachesAptera also serves as a specific epithet in the names of various species:
Apteromantis aptera, a species of praying mantis, endemic to the Iberian Peninsula
Parashorea aptera, a species of plant in the family Dipterocarpaceae, endemic to Indonesia
Hopea aptera, a species of plant in the family Dipterocarpaceae, endemic to Papua New Guinea
Inga aptera, a species of legume in the family Fabaceae, found only in BrazilArchodonata
Archodonata is an extinct order of palaeozoic paleopterous insects, sometimes included in Odonata.Dicondylia
The Dicondylia are a taxonomic group (taxon) that includes all insects except the jumping bristletails (Archaeognatha). Dicondylia have a mandible attached with two hinges to the head capsule (dicondyl), in contrast to the original mandible with a single ball joint (monocondyl).Entognatha
The Entognatha are a class of wingless and ametabolous arthropods, which, together with the insects, makes up the subphylum Hexapoda. Their mouthparts are entognathous, meaning that they are retracted within the head. Entognatha are apterous, meaning that they lack wings. The class contains three orders: Collembola (springtails), Diplura (“two-tail”) and Protura (“first-tail”), and over 5000 known species. These three groups were historically united with the now-obsolete order Thysanura to form the class Apterygota, but it has since been recognized that the hexapodous condition of these animals has evolved independently from that of insects, and independently within each order. The orders may not be closely related, in which case Entognatha would be a polyphyletic group.Eumetabola
Eumetabola is an unranked category of Neoptera. Two large unities known as the Paurometabola and Eumetabola are probably from the adelphotaxa of the Neoptera after exclusion of the Plecoptera. The monophyly of these unities appears to be weakly justified.Insect
Insects or Insecta (from Latin insectum) are hexapod invertebrates and the largest group within the arthropod phylum. Definitions and circumscriptions vary; usually, insects comprise a class within the Arthropoda. As used here, the term Insecta is synonymous with Ectognatha. Insects have a chitinous exoskeleton, a three-part body (head, thorax and abdomen), three pairs of jointed legs, compound eyes and one pair of antennae. Insects are the most diverse group of animals; they include more than a million described species and represent more than half of all known living organisms. The total number of extant species is estimated at between six and ten million; potentially over 90% of the animal life forms on Earth are insects. Insects may be found in nearly all environments, although only a small number of species reside in the oceans, which are dominated by another arthropod group, crustaceans.
Nearly all insects hatch from eggs. Insect growth is constrained by the inelastic exoskeleton and development involves a series of molts. The immature stages often differ from the adults in structure, habit and habitat, and can include a passive pupal stage in those groups that undergo four-stage metamorphosis. Insects that undergo three-stage metamorphosis lack a pupal stage and adults develop through a series of nymphal stages. The higher level relationship of the insects is unclear. Fossilized insects of enormous size have been found from the Paleozoic Era, including giant dragonflies with wingspans of 55 to 70 cm (22 to 28 in). The most diverse insect groups appear to have coevolved with flowering plants.
Adult insects typically move about by walking, flying, or sometimes swimming. As it allows for rapid yet stable movement, many insects adopt a tripedal gait in which they walk with their legs touching the ground in alternating triangles, composed of the front & rear on one side with the middle on the other side. Insects are the only invertebrates to have evolved flight, and all flying insects derive from one common ancestor. Many insects spend at least part of their lives under water, with larval adaptations that include gills, and some adult insects are aquatic and have adaptations for swimming. Some species, such as water striders, are capable of walking on the surface of water. Insects are mostly solitary, but some, such as certain bees, ants and termites, are social and live in large, well-organized colonies. Some insects, such as earwigs, show maternal care, guarding their eggs and young. Insects can communicate with each other in a variety of ways. Male moths can sense the pheromones of female moths over great distances. Other species communicate with sounds: crickets stridulate, or rub their wings together, to attract a mate and repel other males. Lampyrid beetles communicate with light.
Humans regard certain insects as pests, and attempt to control them using insecticides, and a host of other techniques. Some insects damage crops by feeding on sap, leaves, fruits, or wood. Some species are parasitic, and may vector diseases. Some insects perform complex ecological roles; blow-flies, for example, help consume carrion but also spread diseases. Insect pollinators are essential to the life cycle of many flowering plant species on which most organisms, including humans, are at least partly dependent; without them, the terrestrial portion of the biosphere would be devastated. Many insects are considered ecologically beneficial as predators and a few provide direct economic benefit. Silkworms produce silk and honey bees produce honey and both have been domesticated by humans. Insects are consumed as food in 80% of the world's nations, by people in roughly 3000 ethnic groups. Human activities also have effects on insect biodiversity.Metapterygota
Metapterygota is a clade of winged insects containing order Odonata and Infraclass Neoptera.Monura
Monura is an extinct order of wingless insects in the subclass Apterygota. They resembled their modern relatives, the bristletails, and had a single lengthy filament projecting from the end of the abdomen. They also had a pair of leg-like cerci and some non-ambulatory abdominal appendages. The largest specimens reached 30 millimetres (1.2 in) or more, not counting the length of the filament.Myrmeleontoidea
Myrmeleontoidea is a lacewing superfamily in the suborder Myrmeleontiformia.Neoptera
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 (the "Palaeoptera" assemblage), which are unable to flex their wings in this way.Palaeoptera
The name Palaeoptera has been traditionally applied to those ancestral groups of winged insects (most of them extinct) that lacked the ability to fold the wings back over the abdomen as characterizes the Neoptera. The Diaphanopterodea, which are palaeopteran insects, had independently and uniquely evolved a different wing-folding mechanism. Both mayflies and dragonflies lack any of the smell centers in their brain found in Neoptera.Panorpida
Panorpida or Mecopterida is a proposed superorder of Endopterygota. 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 also supported by recent molecular data.Protodiptera
Protodiptera is an extinct order of insects containing the two genera Permotipula and Permila.Psocodea
Psocodea is a taxonomic group of insects comprising the bark lice, book lice and true lice. It was formerly considered a superorder, but is now generally considered by entomologists as an order. Despite the greatly differing appearance of lice, they are believed to have evolved from within the former order "Psocoptera", which contained the bark lice and book lice. Psocodea contains around 11,000 species, divided among seven suborders.Sclerotin
Sclerotin is a component of the cuticles of various Arthropoda, most familiarly insects. It is formed by cross-linking members of particular classes of protein molecules, a biochemical process called sclerotization. Technically it amounts to a form of tanning. The resulting material increases the rigidity of an insect's chitinous exoskeleton. It is particularly prominent in the thicker, armoured parts of insect and arachnid integument, such as in the biting mouthparts and sclerites of scorpions and beetles.As it matures, freshly formed sclerotin becomes a hard, horn-like substance with a range of yellow-brown colors. As animals adapted to life on land, increasingly diverse needs for organic stiffening components arose (as opposed to mineral stiffening components such as calcium carbonates and phosphates). Among the invertebrates this need was met largely by the development of sclerotins and other cross-linked proteins that allowed insects to adapt to existence on the land and later to develop wings.Sclerotin is biochemically variable; different species incorporate different proteins in different proportions, and the same insect will use different compositions in forming the different components of its body. For example, the stiffening of the biting surfaces of a locust's hard mandibles will not be the same as the stiffening of its springy hind tibiae. In general however, it is formed by cross-linking the various protein molecules with phenolic compounds; a tanning process under enzymatic control. In some of the Apterygota however, at least some of the cross-linking is by disulphide bonds reminiscent of protein cross-linking in the formation of keratin. This has led many authors to refer to such cross-linked proteins in invertebrates as keratin, but modern analyses have shown that the term is inappropriate; keratins are a fairly well-defined set of proteins comprising particular chains in different proportions cross-linked in particular ways. Invertebrate connective tissue proteins based on disulphide links appear to be radically different.Silverfish
A silverfish (Lepisma saccharina) is a small, wingless insect in the order Zygentoma (formerly Thysanura). Its common name derives from the animal's silvery light grey colour, combined with the fish-like appearance of its movements. However, the scientific name (L. saccharina) indicates the silverfish's diet consists of carbohydrates such as sugar or starches.Thysanura
Thysanura is the now deprecated name of what was, for over a century, recognised as an order in the class Insecta. The two constituent groups within the former order, the Archaeognatha and the Zygentoma, share several characteristics, such as of having three long caudal filaments, the lateral ones being the cerci, while the one between (telson) is a medial cerciform appendage, specifically an epiproct. They are also both wingless, and have bodies covered with fine scales, rather like the scales of the practically unrelated Lepidoptera. In the late 20th century, it was recognized that the two suborders were not sister taxa, therefore Thysanura was paraphyletic, and the two suborders were each raised to the status of an independent monophyletic order, with Archaeognatha sister taxon to the Dicondylia, including the Zygentoma.
Although the group Thysanura is no longer recognized, the name still appears in some published material. Another name used to separate the two groups from winged insects is Apterygota.
Extant Arthropoda classes by subphylum