Idiosoma
genus of arachnids
Idiosoma is a genus of Australian armoured trapdoor spiders that was first described by Anton Ausserer in 1871. Originally placed with the Ctenizidae, it was moved to the armoured trapdoor spiders in 1985. The name is derived from the Greek ἴδιος (idios), meaning "individual, unique", and σῶμα (soma), meaning "body", referring to the distinctive structure of the abdomen.
Description
The skin of their abdomen is hardened, with a flattened end and deep grooves running along the sides. The thickened skin helps to reduce water loss in its dry habitat. It also serves as a kind of plug to shield itself from predators. This phenomenon is called phragmosis and occurs in perfection in the spider genus Cyclocosmia (Ctenizidae). However, some parasitic wasps have evolved paper-thin abdomens and long, slender ovipositors and lay their eggs on the softer skin at the front of the spider's abdomen.
Females of the black rugose trapdoor spider (Idiosoma nigrum) can grow up to 30 millimetres (1.2 in) long. Males can grow up to 18 millimetres (0.71 in) in body length.
This brief starts where responsible research should: with the source description of “Idiosoma” as genus of arachnids. Everything that follows is an evidence route, not borrowed authority.
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The subject matters to the science & nature register because the source frames it as genus of arachnids. Its deeper value depends on whether names, dates, institutions and citations support that framing.
The date and method of observation matter as much as the stated conclusion, especially where classification or consensus has changed. The source revision retrieved here is dated Nov 11, 2025. The linked authority identifier is Q3018006. The first chronological checks are 1871 and 1985.
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This entry incorporates text from “Idiosoma” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.