''Tricholepidion'' is a genus of wingless insect belonging to

Zygentoma Zygentoma are an order in the class Insecta, and consist of about 550 known species. The Zygentoma include the so-called silverfish or fishmoths, and the firebrats. A conspicuous feature of the order are the three long caudal filaments. The t ...

( silverfish and allies), with only a single described species ''T. gertschi,'' native to the northern coast of California in Western North America. It lives under dead bark and in rotting wood of conifers in

mesophytic Mesophytes are terrestrial plants which are neither adapted to particularly dry nor particularly wet environments. An example of a mesophytic habitat would be a rural temperate meadow, which might contain goldenrod, clover, oxeye daisy, and ''Rosa m ...

forests. It is alternatively considered the only living member of the family

Lepidotrichidae Lepidotrichidae is a family of basal insects belonging to the order Zygentoma ( silverfish and allies) The family contains the extinct '' Lepidotrix'', known from specimens preserved in Eocene The Eocene ( ) Epoch is a geological epoch tha ...

, which also includes ''

Lepidotrix ''Lepidotrix'' is an extinct genus of wingless insect belonging to Zygentoma (silverfish and allies) in the family Lepidotrichidae. There is one described species in ''Lepidotrix'', ''L. piliferum/pillifera''. It is known from specimens found ...

'' from

Eocene The Eocene ( ) Epoch is a geological epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The name ''Eocene'' comes from the Ancient Greek (''ēṓs'', " ...

aged European amber, or the only member of the family Tricholepidiidae. The taxonomic position of ''Tricholepidion'' is uncertain, in some

molecular phylogenetics Molecular phylogenetics () is the branch of phylogeny that analyzes genetic, hereditary molecular differences, predominantly in DNA sequences, to gain information on an organism's evolutionary relationships. From these analyses, it is possible to ...

studies it has been recovered as less closely related to

flying insects The Pterygota ( grc, πτερυγωτός, pterugōtós, winged) are a subclass of insects that includes the winged insects. It also includes insect orders that are secondarily wingless (that is, insect groups whose ancestors once had wings b ...

(Pterygota) than the rest of Zygentoma is, rendering Zygentoma paraphyletic. Each compound eye contains ~40 ommatidia, and they have three ocelli. Scales on the body are absent. Unlike

Archaeognatha 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 ...

and the other families of Zygentoma, which have three- and sometimes two-segmented tarsi, they have five-segmented tarsi like many winged insects.Evolution of the Insects
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References

Further reading