Orsonwelles

Orsonwelles is a genus of American dwarf spiders that was first described by G. Hormiga in 2002.[2] They are all native to the Hawaiian Islands, each species occurring on a single island, often at high elevations. One species has not been collected since the 1890s, and is believed to be extinct. The name honors the actor and film-maker Orson Welles. Many of the species names commemorate elements from Welles' films, radio productions, or roles.

Orsonwelles
Orsonwelles graphicus
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Subphylum: Chelicerata
Class: Arachnida
Order: Araneae
Infraorder: Araneomorphae
Family: Linyphiidae
Genus: Orsonwelles
Hormiga, 2002[1]
Type species
O. polites
Hormiga, 2002
Species

13, see text

Range of Orsonwelles in the Hawaiian Islands

The first species were described in 1900 by the French naturalist Eugène Simon, who described Orsonwelles malus (as Labulla torosa) and Orsonwelles graphicus (as Labulla graphica).[3] In 2002, Gustavo Hormiga described eleven new species, establishing the new genus Orsonwelles. The Labulla species became torosus and graphicus because Orsonwelles is a masculine noun.[2]

Description

The carapace and abdomen are dark brown to gray. A light band runs down the middle of the carapace. The abdomen is oval-shaped, and sometimes has light blotches or chevron-shaped markings on the dorsal surface. The second limb segments on the third and fourth leg pairs have one to six trichobothria, a trait unique among the Linyphiidae. Their chelicerae are massive and have many cheliceral teeth.[2]

They are nocturnal, remaining hidden during the day and appearing upside down in the center of their webs at night. Large chelicerae with teeth allow them to be generalist predators, feeding on a variety of arthropods, including moths and terrestrial amphipods.[2] Several species of Argyrodes, a genus of smaller spiders and occasional kleptoparasites of Orsonwelles, have been found caught in their webs.[4]

They primarily live in remnants of rainforests and mixed mesic forests. Many are restricted to higher elevations, where environmental disturbance is less severe and non-native species less common, but some species occur in disturbed areas as low as 500 m (1,600 ft) above sea level.[2]

In part, due to island gigantism, a phenomenon causing lineages on islands to evolve larger than their mainland relatives, Orsonwelles contains the largest known members of the family Linyphiidae. Females reach body lengths of 8.06 to 14.07 millimetres (0.317 to 0.554 in), and males reach 6.2 to 11.35 millimetres (0.244 to 0.447 in). The largest individuals recorded are in the species O. malus. The next largest is Laminacauda gigas, attaining body lengths of just under 10 millimetres (0.39 in).[2]

Species

Each species is endemic to a single island, with six species on Kauai , three on Oahu, two on Molokai, and one on Maui and the Island of Hawaii.[2][5] The species O. torosus of Kauai is believed to be extinct, as it was last collected in the 1890s and has not been collected since.

As of May 2019 it contains thirteen species:[1]

See also

References
  1. Gloor, Daniel; Nentwig, Wolfgang; Blick, Theo; Kropf, Christian (2019). "Gen. Orsonwelles Hormiga, 2002". World Spider Catalog Version 20.0. Natural History Museum Bern. doi:10.24436/2. Retrieved 2019-06-16.
  2. Hormiga, G. (2002). "Orsonwelles, a new genus of giant linyphiid spiders (Araneae) from the Hawaiian Islands" (PDF). Invertebrate Systematics. 16 (3): 369–448. doi:10.1071/IT01026.
  3. Simon, E. (1900), "Arachnida", in Sharp, D. (ed.), Fauna Hawaiiensis, or the zoology of the Sandwich Isles: being results of the explorations instituted by the Royal Society of London promoting natural knowledge and the British Association for the Advancement of Science, University Press, Cambridge, pp. 463–464, retrieved 2020-05-18
  4. Rivera, Malia; Gillespie, Rosemary G. (2010). "New species of endemic kleptoparasitic spiders of the genus Argyrodes (Araneae: Theridiidae) in the Hawaiian Islands" (PDF). Pacific Science. 64 (2): 221–231. doi:10.2984/64.2.221. hdl:10125/23103.
  5. Hormiga, Gustavo; Arnedo, Miquel; Gillespie, Rosemary G. (2003). "Speciation on a Conveyor Belt: Sequential Colonization of the Hawaiian Islands by Orsonwelles Spiders (Araneae, Linyphiidae)". Systematic Biology. 52 (1): 70–88. doi:10.1080/10635150390132786. PMID 12554442.
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