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| regnum = Animalia | phylum = Arthropoda | subphylum = Hexapoda | classis = Insecta | subclassis = Monocondylia | subclassis_authority = Haeckel, 1866 | ordo = Archaeognatha | ordo_authority = Börner, 1904 | subdivision_ranks = Families | subdivision = *Machilidae *Meinertellidae }} The Archaeognatha are an order of wingless insects, also known as jumping bristletails. They are among the least evolutionarily changed insects, appearing in the Middle Devonian period along with the arachnids. They are known from both body and trace fossils (the latter including body imprints and trackways) throughout the remainder of the Paleozoic Era. The name Archaeognatha is derived from Greek, ''archaeos'' meaning "ancient" and ''gnatha'' meaning "jaw". This refers to the articulation of the mandibles, which has a single condyle, where all higher insects have two. An alternate name, Microcoryphia, comes from the Greek ''micro'', meaning "small", and ''coryphia'', meaning head. The order Archaeognatha has previously been combined with the order Thysanura; both orders possess three-pronged tails comprising two cerci and an epiproct. The approximately 350 species in the two families are distributed worldwide. No species is currently at conservation risk. ==Description== Archaeognaths are small insects with elongated bodies bent into an arch shape and three long tail-like structures, of which the median filament is longest. They have flexible antennae, large compound eyes that meet at the top of the head, and three ocelli. Their mouthparts are partially retractable, with simple chewing mandibles and long maxillary palps. Archaeognatha differ from Thysanura in being able to use their tails to spring up to into the air. They are also unique in possessing small, articulated "styli" on the hind (and sometimes middle) coxae and sternites 2 to 9, which are sometimes considered to be rudimentary appendages, as well as paired eversible membranous vesicles through which they absorb water. Further unusual features are that the abdominal sternites are each composed of three sclerites, and they cement themselves to the substrate before molting. Like Thysanura, the body is covered with scales, with a thin exoskeleton that is susceptible to dehydration. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Archaeognatha」の詳細全文を読む スポンサード リンク
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