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.[1][2]

Fancy Bristletail - Flickr - treegrow (2)
A typical member of the order Archaeognatha

Although the group Thysanura is no longer recognized, the name still appears in some published material.[3] Another name used to separate the two groups from winged insects is Apterygota.


The name Thysanura was derived from the Greek θυσάνος, thysanos for fringe, tassel, bristle and οὐρά, oura for "tail", a reference to the three fanned out caudal filaments. This etymology is consistent with the English word "bristletail", which is the common name for several hexapod species, not all of which fell within Thysanura.[4]


  1. ^ A. Blanke, M. Koch, B. Wipfler, F. Wilde, B. Misof (2014) Head morphology of Tricholepidion gertschi indicates monophyletic Zygentoma. Frontiers in Zoology 11:16 doi:10.1186/1742-9994-11-16
  2. ^ P. J. Gullan; P. S. Cranston (13 July 2010). The Insects: An Outline of Entomology. John Wiley & Sons. pp. 202–. ISBN 978-1-4443-1767-1.
  3. ^ Richards, O.W.; Davies, R.G. (1977). Imms' General Textbook of Entomology: Volume 1: Structure, Physiology and Development Volume 2: Classification and Biology. Berlin: Springer. ISBN 0-412-61390-5.
  4. ^ Eric Tentarelli (2012). A Guide to Insects. Blackwell. p. 220.
  • Grimaldi, D. and Engel, M.S. (2005). Evolution of the Insects. Cambridge University Press. ISBN 0-521-82149-5.CS1 maint: Multiple names: authors list (link)
  • Charles A. Triplehorn and Norman F. Johnson, Borror and DeLong's Introduction to the Study of Insects, 7th edition (Thomas Brooks/Cole, 2005), pp. 177–180
  • Firefly Encyclopedia of Insects and Spiders, edited by Christopher O'Toole, ISBN 1-55297-612-2, 2002

External links


Allacrotelsa is a genus of primitive insects belonging to the family Lepismatidae.


Ametabolism is a type of growth or life cycle in insects in which there is slight or no metamorphosis, only a gradual increase in size. It is present only in primitive wingless insects, e.g. order: Thysanura (Silverfish).


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.

The nymphs (younger stages) go through little or even no metamorphosis, hence they resemble the adult specimens. Their skin is thin, making them appear translucent.

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.


The Archaeognatha are an order of apterygotes, known by various common names such as jumping bristletails. Among extant insect taxa they are some of the most evolutionarily primitive; they appeared in the Middle Devonian period at about the same time as the arachnids. Specimens that closely resemble extant species have been found as both body and trace fossils (the latter including body imprints and trackways) in strata from the remainder of the Paleozoic Era and more recent periods. For historical reasons an alternative name for the order is Microcoryphia.Until the late 20th century the suborders Zygentoma and Archaeognatha comprised the order Thysanura; both orders possess three-pronged tails comprising two lateral cerci and a medial epiproct or appendix dorsalis. Of the three organs, the appendix dorsalis is considerably longer than the two cerci; in this the Archaeognatha differ from the Zygentoma, in which the three organs are subequal in length. In the late 20th century, it was recognized that the order Thysanura was paraphyletic, thus the two suborders were each raised to the status of an independent monophyletic order, with Archaeognatha sister taxon to the Dicondylia, including the Zygentoma.The order Archaeognatha is cosmopolitan; it includes roughly 500 species in two families. No species is currently evaluated as being at conservation risk.


Atelura is a genus of primitive insects belonging to the order Thysanura.


Atelurinae is a subfamily of primitive insects belonging to the order Zygentoma. Once considered an independent family, it is now treated as a subfamily within the Nicoletiidae. They are generally found in association with ants or termites, living as inquilines in the hosts' nests. They are typically small, tear-drop or sub-ovoid in body shape, light yellow in color and lacking eyes. The subfamily is quite diverse, with more than 140 described species in about 70 genera; many of the genera are monotypic.

Bookworm (insect)

Bookworm is a general name for any insect that is said to bore through books.The damage to books that is commonly attributed to "bookworms" is, in truth, not caused by any species of worm. Often, the larvae of various types of insects including beetles, moths and cockroaches, which may bore or chew through books seeking food, are responsible. Some such larvae exhibit a superficial resemblance to worms and are the likely inspiration for the term, though they are not true worms. In other cases, termites, carpenter ants, and woodboring beetles will first infest wooden bookshelves and later feed on books placed upon the shelves, attracted by the wood-pulp paper used in most commercial book production.

True book-borers are uncommon. The primary food sources for many "bookworms" are the leather or cloth bindings of a book, the glue used in the binding process, or molds and fungi that grow on or inside books. When the pages themselves are attacked, a gradual encroachment across the surface of one page or a small number of pages is typical, rather than the boring of holes through the entire book (see images on right).The term has come to have a second, idiomatic use, indicative of a person who reads a great deal or to perceived excess: someone who devours books metaphorically.


Ctenolepisma is a genus of primitive insects (order Zygentoma = Thysanura s.s.) closely related to the silverfish and firebrat but less reliant on human habitation, some species being found both indoors and outdoors and some found exclusively outdoors. The genus is distributed nearly worldwide in warm regions. Australia lacks native Ctenolepisma, but is home to introduced species.


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).


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 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.


Lepidotrichidae is a family of basal insects belonging to the order Zygentoma. The family is considered to contain two genera: the extinct Lepidotrix, known from specimens preserved in Baltic amber, and the extant Tricholepidion, which contains a single species, Tricholepidion gertschi. This species is an example of a living fossil, the one remaining member of a clade which was once widespread. Recent research has suggested the extant species should be assigned to its own family, Tricholepidiidae.


Maindroniidae is a very small family of basal insects belonging to the order Thysanura. It contains just a single genus, Maindronia, and a handful of species.

These distinctive insects are strictly coastal, being found along the arid coastline of Peru and Chile among seaweed.


Neoasterolepisma is a genus of primitive insects belonging to the family Lepismatidae. Many species live with ants.


Nicoletiidae is a family of primitive insects belonging to the order Zygentoma. These insects live primarily underground, under detritus, or in caves. A few species are recorded as commensals inside nests of social insects, such as the species Allotrichotriura saevissima which lives inside fire ant nests.


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.


Thermobia is a genus of primitive insects belonging to the family Lepismatidae. By far the best known member of the genus is the firebrat T. domestica, which is often seen in warm places indoors such as bakeries.


Tricholepisma is a genus of primitive insects belonging to the family Lepismatidae.


Zygentoma are an order in the class Insecta, and consist of about 400 known species. The Zygentoma include the so-called silverfish or fishmoths, and the firebrats. A conspicuous feature of the order is that the members all have three long caudal filaments. The two lateral filaments are cerci, and the medial one is an epiproct or appendix dorsalis. In this they resemble the Archaeognatha, though, unlike in the latter order, the cerci of Zygentoma are nearly as long as the epiproct.Until the late twentieth century the Zygentoma were regarded as a suborder of the Thysanura, until it was recognized that the order Thysanura was paraphyletic, thus the two suborders were each raised to the status of an independent monophyletic order, with Archaeognatha sister taxon to the Dicondylia, including the Zygentoma.

Insect orders
Extant Thysanura families


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