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arachnid
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A brown Buthus scorpion with its tail arched over its back and stinger raised, standing on a piece of wood. Illustration showing eight types of mites and ticks, each labeled with their common and scientific names, including tropical rat mite, Opilioacarus texanus, Holothyrus legendrei, fur mite, black-legged tick, soil mite, itch mite, and American house-dust mite. Chart titled Diversity of arachnids comparing a Silurian fossil scorpion and 11 living groups, including spiders, scorpions, mites, daddy longlegs, sunspiders, whip scorpions, and false scorpions. Illustrations show their varied forms and typical size ranges from 0.1 millimeters to 210 millimeters; fossil anatomy labels identify pincers, pedipalps, legs, and body sections. Tailless whip scorpion Illustration of a ricinuleid, a small arachnid in the order Ricinulei, showing its segmented brown body, eight jointed legs, and distinctive shield-like structure on its back. Illustration of a palpigrade arachnid (order Palpigradi), showing its small, segmented body, eight legs, and a long, thin, bristle-covered tail. Size range is 0.8 to 2.6 millimeters. Illustration of a daddy longlegs, or Opiliones, showing its small, rounded body and extremely long, thin legs, characteristic of this arachnid order. A detailed top view of a schizomid arachnid (order Schizomida), showing its segmented, striped abdomen, elongated legs, and small pincers, measuring about 5 to 7 millimeters long.
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arachnid: References & Edit History

Article History

Type Description Contributor Date
Invalidated site: Smithsonian Libraries and Archives - DSpace Repository - Arachnids. Oct 16, 2026
Add new Web site: Digital Commons at Michigan Tech - Arthropods: Arachnida - Spider Biology (PDF). Jan 31, 2026
Questions and answers added. Dec 24, 2025
Revised opening paragraph. Added media throughout. Dec 17, 2025
Add new Web site: K12 LibreTexts - Arachnids. Jul 19, 2025
Add new Web site: Portland State University - Arachids. Apr 13, 2025
Add new Web site: Academia - Arachnida (PDF). Feb 25, 2025
Add new Web site: Smithsonian Libraries and Archives - DSpace Repository - Arachnids. Sep 27, 2024
Media added. May 29, 2024
Add new Web site: National Center for Biotechnology Information - PubMed Central - Recent progress and prospects for advancing arachnid genomics. Apr 10, 2024
Add new Web site: Animal Corner - Arachnid. Dec 08, 2023
Add new Web site: Brandeis University - Life Sciences - Introduction to Arachnids. Aug 21, 2023
Add new Web site: National Center for Biotechnology Information - PubMed Central - Recent progress and prospects for advancing arachnid genomics. May 05, 2023
Add new Web site: Frontiers - Frontiers in Arachnid Science - The seven grand challenges in arachnid science. Feb 25, 2023
Add new Web site: CALS Encyclopedia of Arkansas - Arachnid. Sep 30, 2022
Media added. Apr 12, 2018
Add new Web site: BioKIDS - Arachnida. Feb 28, 2017
Add new Web site: Animal Planet - Arachnid. Oct 21, 2013
Added image of tailless whip scorpion. Mar 22, 2013
Art depicting the diversity of arachnids added. Oct 26, 2012
Classification section updated to reflect taxonomic changes affecting subclass Acari. Nov 15, 2011
Added illustrations of different types of arachnids. Nov 15, 2011
Geologic time data updated. Sep 01, 2009
Added new Web site: Enchanted Learning - Arachnid Printouts. May 27, 2009
Media added. Sep 12, 2008
Added new Web site: Australian Museum - Arachnids. Jul 06, 2008
Added new Web site: Official Site of City of Arao, Japan. May 21, 2008
Article revised. Jul 15, 2005
Article revised. Sep 05, 2000
Article added to new online database. Jul 26, 1999
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