Arthropods Codexery

Opiliones

Harvestmen are arachnids with fused bodies and no venom.

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Opiliones, commonly called harvestmen or daddy longlegs, are an order of arachnids distinct from spiders.[1][2] As of December 2019, the World Catalogue of Opiliones listed over 6,650 discovered species, and the actual number of living species may be more than 10,000.[1][3]

Scientific classification

  1. KingdomAnimalia
  2. PhylumArthropoda
  3. SubphylumChelicerata
  4. ClassArachnida
  5. OrderOpiliones

Named by Sundevall, 1833

Sources: Wikipedia taxobox: Opiliones (CC BY-SA 4.0)

Key facts and history

Most harvestmen have a single pair of camera-type eyes on the head, but Cyphophthalmi have lateral eyes when present.[4] Typical body length is under 7 mm, though Trogulus torosus reaches 22 mm, and leg spans can exceed 160 mm.[5] Many species are omnivorous, eating insects, plant material, and fungi, which is unusual among arachnids.[6] Most harvestmen reproduce sexually, with direct copulation except in small fossorial Cyphophthalmi.[7]

Some species practice paternal care, with males guarding eggs from multiple partners.[8] Harvestmen lack venom glands and cannot bite humans, contrary to urban legends.[9] Fossil harvestmen discovered in 400-million-year-old cherts from Scotland and in 305-million-year-old rocks from France appear very similar to modern forms, indicating that their basic body shape developed early and has remained largely unchanged in some groups.[10] The Devonian fossil Eophalangium sheari, which is 410 million years old, already possessed tracheae and sexual organs, as shown by a female specimen with an ovipositor and a male with a penis.[11][12]

According to a molecular phylogenetic analysis published in 2014, the Opiliones order originated approximately 473 million years ago, which places its emergence in the Ordovician period.[13] In 2014, researchers reported a 305-million-year-old fossil harvestman that had two pairs of eyes; subsequent work identified this four-eyed fossil as most likely belonging to the suborder Eupnoi.[4][14]

What the cited sources add

A 2014 LiveScience article reported that a 305-million-year-old fossil from eastern France had two separate sets of eyes, one central and one lateral.[15] The same source noted that harvestmen are more closely related to scorpions than to spiders.[15] A Christian Science Monitor article from 2014 described the discovery of a four-eyed harvestman fossil as a previously unknown species.[16] The World Catalogue of Opiliones, updated to December 2019, provides a taxonomic backbone for the order.[3]

References

  1. Wikipedia, "Opiliones" (CC BY-SA 4.0), which cites: "Opiliones", Kury, A. et al. (2023). WCO-Lite: World Catalogue of Opiliones; Kury, "Classification of Opiliones", www.museunacional.ufrj.br; "Opiliones", Joel Hallan's Biology Catalog (Archive version. August 2017); Glauco Machado, Ricardo Pinto-da-Rocha & Gonzalo Giribet, "Harvestmen: the Biology of Opiliones", Harvard University Press, 2007, p. 1–13; Garwood, "A Paleozoic Stem Group to Mite Harvestmen Revealed through Integration of Phylogenetics and Development", Current Biology, 2014, p. 1017–1023 (we also read that source) en.wikipedia.org
  2. Wikipedia, "Opiliones" (CC BY-SA 4.0), which cites: Ballesteros, "A Critical Appraisal of the Placement of Xiphosura (Chelicerata) with Account of Known Sources of Phylogenetic Error", Systematic Biology, 2019-11-01, p. 896–917; Ballesteros, "Comprehensive Species Sampling and Sophisticated Algorithmic Approaches Refute the Monophyly of Arachnida", Molecular Biology and Evolution, 2022-02-03 (original not read by us) en.wikipedia.org
  3. "Opiliones", Kury, A. et al. (2023). WCO-Lite: World Catalogue of Opiliones. facts only, no text reused. wcolite.com
  4. Wikipedia, "Opiliones" (CC BY-SA 4.0), which cites: Blaszczak-Boxe, "4-Eyed Daddy Longlegs Helps Explain Arachnid Evolution (Video)", livescience.com, 2014-04-10; Garwood, "A Paleozoic Stem Group to Mite Harvestmen Revealed through Integration of Phylogenetics and Development", Current Biology, 2014, p. 1017–1023; Pinto-da-Rocha, "Third species of Guasiniidae (Opiliones, Laniatores) with comments on familial relationships", Journal of Arachnology, 2003, p. 394–399; Gainett, "Vestigial organs alter fossil placements in an ancient group of terrestrial chelicerates", Current Biology, February 202 en.wikipedia.org
  5. Wikipedia, "Opiliones" (CC BY-SA 4.0), which cites: Glauco Machado, Ricardo Pinto-da-Rocha & Gonzalo Giribet, "Harvestmen: the Biology of Opiliones", Harvard University Press, 2007, p. 1–13; "SENCKENBERG world of biodiversity | About us | Communications | Newsroom" (original not read by us) en.wikipedia.org
  6. Wikipedia, "Opiliones" (CC BY-SA 4.0), which cites: Glauco Machado, Ricardo Pinto-da-Rocha & Gonzalo Giribet, "Harvestmen: the Biology of Opiliones", Harvard University Press, 2007, p. 1–13 (original not read by us) en.wikipedia.org
  7. Wikipedia, "Opiliones" (CC BY-SA 4.0), which cites: Cowles, "Amazing Arachnids", Princeton University Press, 2018-06-12 (we also read that source) en.wikipedia.org
  8. Wikipedia, "Opiliones" (CC BY-SA 4.0), which cites: Machado, "Parental investment and the evolution of subsocial behaviour in harvestmen (Arachnida: Opiliones)", Ethology Ecology & Evolution, 2001, p. 133–150; Nazareth, "Reproductive Behavior of Chavesincola inexpectabilis (Opiliones, Gonyleptidae) with Description of a New and Independently Evolved Case of Paternal Care in Harvestmen", The Journal of Arachnology, 2009, p. 127; Machado, "Reproductive Behavior in Harvestman (Arachnida): Mating Systems and Parental Care", Oecologia Australis, 2009-12-06, p. 58–79 (original not read by us) en.wikipedia.org
  9. Wikipedia, "Opiliones" (CC BY-SA 4.0), which cites: Berenbaum, "The Earwig's Tail: a modern bestiary of multi-legged legends", Harvard University Press, 30 September 2009, p. 143; The Spider Myths Site: "Daddy-Longlegs" (original not read by us) en.wikipedia.org
  10. Wikipedia, "Opiliones" (CC BY-SA 4.0), which cites: Garwood, "Anatomically modern Carboniferous harvestmen demonstrate early cladogenesis and stasis in Opiliones", Nature Communications, 2011 (original not read by us) en.wikipedia.org
  11. Wikipedia, "Opiliones" (CC BY-SA 4.0), which cites: Glauco Machado, Ricardo Pinto-da-Rocha & Gonzalo Giribet, "Harvestmen: the Biology of Opiliones", Harvard University Press, 2007, p. 1–13; Garwood, "Anatomically modern Carboniferous harvestmen demonstrate early cladogenesis and stasis in Opiliones", Nature Communications, 2011; Perkins, "Long-lasting daddy longlegs", June 23, 2009; Diying Huang, Paul A. Selden & Jason A. Dunlop, "Harvestmen (Arachnida: Opiliones) from the Middle Jurassic of China", Naturwissenschaften, 2009, p. 955–962 (original not read by us) en.wikipedia.org
  12. Wikipedia, "Opiliones" (CC BY-SA 4.0), which cites: Garwood, "A Paleozoic Stem Group to Mite Harvestmen Revealed through Integration of Phylogenetics and Development", Current Biology, 2014, p. 1017–1023; Tepper, "Ancient four-eyed wonder resolves daddy longleg mystery", Christian Science Monitor, April 11, 2014; Gainett, "Vestigial organs alter fossil placements in an ancient group of terrestrial chelicerates", Current Biology, February 2024, p. 1258–1270.e5 (we also read that source) en.wikipedia.org
  13. Wikipedia, "Opiliones" (CC BY-SA 4.0), which cites: Sharma, "A revised dated phylogeny of the arachnid order Opiliones", Frontiers in Genetics, 2014, p. 255 (original not read by us) en.wikipedia.org
  14. Wikipedia, "Opiliones" (CC BY-SA 4.0), which cites: Gainett, "Vestigial organs alter fossil placements in an ancient group of terrestrial chelicerates", Current Biology, February 2024, p. 1258–1270.e5 (original not read by us) en.wikipedia.org
  15. Blaszczak-Boxe, "4-Eyed Daddy Longlegs Helps Explain Arachnid Evolution (Video)", livescience.com, 2014-04-10. facts only, no text reused. livescience.com
  16. Tepper, "Ancient four-eyed wonder resolves daddy longleg mystery", Christian Science Monitor, April 11, 2014. facts only, no text reused. csmonitor.com

Each numbered sentence above was checked against the source it cites before publication. Sentences citing Wikipedia adapt text from the English Wikipedia article Opiliones (contributors), used under CC BY-SA 4.0; this entry is available under the same licence. Other sources were used for facts only; no text or images are copied from them.

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Compiled from Wikipedia and the sources listed below. Text from Wikipedia is available under CC BY-SA 4.0; this entry is adapted from it.

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