Wikipedia

Theridion

Theridion is a genus of tangle-web spiders with a worldwide distribution.[6] Notable species are the Hawaiian happy face spider (T. grallator), named for the iconic symbol on its abdomen, and T. nigroannulatum, one of few spider species that lives in social groups, attacking prey en masse to overwhelm them as a team.

Theridion
Temporal range: Cretaceous–present
male T. grallator
T. pictum
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Arthropoda
Subphylum: Chelicerata
Class: Arachnida
Order: Araneae
Infraorder: Araneomorphae
Family: Theridiidae
Genus: Theridion
Walckenaer, 1805
Type species
Aranea picta
Walckenaer, 1802[1]
Species

T. attritum
T. grallator
T. nigroannulatum
T. strepitus
 hundreds more, see text.

Diversity
nearly 600 species
Synonyms

Identification

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Spiders in this genus are about as long or longer than they are wide. Their chelicerae have two or less teeth on the front edge and none on the back edge. The front leg is the longest in both genders, but the next longest is the second leg in males and the fourth leg in females. The epigyne can vary, but the pedipalp has a median apophysis and a colulus is absent from both genders.[7] In several species, the males have mastidia (projections) on the chelicerae.[8]

Theridion has the anterior eye row slightly curved and with a gap between it and the posterior eye row. This distinguishes it from Enoplognatha, another theridiid genus in which the anterior eye row is almost straight and the gap between eye rows is very small.[8]

Ecology

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Theridion build tangle webs, usually under leaves and among vegetation. At night, spiders hang upside-down in these webs. During the day, they hide close by their webs.[9]

Philodromus cespitum, a species of running crab spider, preys on Theridion spiders in European fruit orchards.[10]

Mating

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Mating behaviour has been studied in several Theridion species. It involves pseudocopulation, numerous sperm inductions and copulatory sequences. The male approaches the female to mate, usually in the latter's retreat (a hood-shaped part of the web where the female lives in). Male Theridion perform contralateral insertions, inserting their left palp into the female's right introductory duct and vice versa for the right palp. Female Theridion are less aggressive after mating compared to other genera of theridiids.[11]

Species

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There are almost 600 described species of Theridion.[6] However, the genus has traditionally been assigned species that lack a colulus and did not fit into other genera (wastebasket taxon).[9][12] New species continue to be described on a regular basis.[9][12]

References

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  1. ^ "Theridion pictum (Walckenaer, 1802)". World Spider Catalog. 20.0. Natural History Museum Bern. 2019. Retrieved 14 April 2019.
  2. ^ Levi, H. W. (1957). "The spider genera Enoplognatha, Theridion, and Paidisca in America north of Mexico (Araneae, Theridiidae)". Bulletin of the American Museum of Natural History. 112: 1–124.
  3. ^ Levi, H. W. (1967d). The spider genus Billima Simon. Psyche: A Journal of Entomology 74: 340-341
  4. ^ Miller, J. A. (2007). "Review of erigonine spider genera in the Neotropics (Araneae: Linyphiidae, Erigoninae)". Zoological Journal of the Linnean Society. 149: 1–263. doi:10.1111/j.1096-3642.2007.00233.x.
  5. ^ Levi, H. W.; Levi, L. R. (1962). "The genera of the spider family Theridiidae". Bulletin of the Museum of Comparative Zoology. 127.
  6. ^ a b "NMBE - World Spider Catalog". wsc.nmbe.ch. Retrieved 2022-09-05.
  7. ^ Levi, H. W. (1963). "American spiders of the genus Theridion (Araneae, Theridiidae)". Bulletin of the Museum of Comparative Zoology. 129.
  8. ^ a b "Genus Theridion". bugguide.net. Retrieved 2022-09-05.
  9. ^ a b c Bellvert, Adrià; Gillespie, Rosemary G.; Arnedo, Miquel A. (2021). "A happy family: systematic revision of the endemic Theridion spiders (Araneae, Theridiidae) of the Hawaiian Islands". Invertebrate Systematics. 35 (1): 1–58. doi:10.1071/IS20001. ISSN 1445-5226. S2CID 231938492.
  10. ^ Michalko, Radek; Dvoryankina, Viktoriya (1 June 2019). "Intraspecific phenotypic variation in functional traits of a generalist predator in an agricultural landscape". Agriculture, Ecosystems & Environment. 278: 35–42. doi:10.1016/j.agee.2019.03.018.
  11. ^ Knoflach, Barbara (1998). "Mating in Theridion varians Hahn and related species (Araneae: Theridiidae)". Journal of Natural History. 32 (4): 545–604. Bibcode:1998JNatH..32..545K. doi:10.1080/00222939800770301. ISSN 0022-2933.
  12. ^ a b Domènech, Marc; Crespo, Luís C.; Enguídanos, Alba; Arnedo, Miquel A. (2020-04-05). "Mitochondrial discordance in closely related Theridion spiders (Araneae, Theridiidae), with description of a new species of the T. melanurum group". Zoosystematics and Evolution. 96 (1): 159–173. doi:10.3897/zse.96.49946. ISSN 1860-0743. S2CID 218920405.
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