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Evarcha striolata

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Taxonomy and etymology

Evarcha striolata is a species of jumping spider, a member of the family Salticidae, that was first described by the arachnologists Wanda Wesołowska and Charles Haddad in 2009.[1] Named for a Latin word for a "striped", it was one of over 500 species identified by the Polish arachnologist Wesołowska during her career, making her one of the most prolific in the field.[2][3] They allocated it to the genus Evarcha, which had been first circumscribed by Eugène Simon in 1902.[4]

The genus is closely related to the genera Hyllus and Plexippus.[5] Analysis of protein-coding genes showed it was particularly related to Telamonia.[6] In 2016, Jerzy Prószyński added the genus to a group of genera named Evarchines, named after the genus, along with Hasarinella and Nigorella based on similarities in the spiders' copulatory organs.[7]

Prószyński placed the spider in a new genus Evacin in 2018 based on its copulatory organs and the way that they differ from other Evarcha spiders.[8] The new genus name is a combination of Evacha and flavocin.[9] This designation is not widely accepted and the species remains in the Evarcha genus in the World Spider Catalog.[1][10]

Description

Evarcha striolata is a medium-sized spider with looks that are typical for the genus. It has a body divided into two main parts: a rectangular cephalothorax and thinner, more oval abdomen.{[11] The male has a carapace, the hard upper side of the cephalothorax, that is typically 2.1 mm (0.08 in) long and 1.6 mm (0.06 in) wide. Generally rather high with a sharply sloping back.it is generally dark orange and hairless with dark rings around the eyes. There are a few delicate bristles near the front eyes. The underside of the cephalothorax, or sternum, is dark yellow. The spider's clypeus, or face, is low and is decorated with a scattering of delicate hairs. The mouthparts, including the chelicerae, labium and maxillae, are dark yellow.[2]

The male spider's abdomen is narrower than its carapace, measuring typically 2 mm (0.08 in) in length and having a width of typically 1.1 mm (0.04 in).The topside has a distinctive striped pattern, with two brown streaks formed of dark hairs running down the abdomen from front to back, divided by three yellow streaks.[2] It lacks the scutum on the back that marks out the similar Evarcha flagellaris'.[12] There are dark streaks on the sides while the underside is light yellow with a pattern of two thin dark lines running from front to back crossed by another line that runs across near the pale spinnerets. The spider has yellowish legs that have a covering of short brown hairs and a relatively large number of spines. The pedipalps are pale.[2]

The spider's copulatory organs are similar to other species in the genus, particularly those found in Australia, like Evarcha infrastriata, and Asia, like Evarcha flavocincta and Evarcha kochi. [2][13] The last of those is the type species for the genus Evacin.[9] Evarcha striolata has male copulatory organs that include a round hemispherical tegulum that has a long thin embolus attached to the side. The embolus follows the curve of the palpal bulb until it reaches the top, at which point it projects towards the cymbium that surrounds the tegulum. At the base of the tegulum is palpal tibia, which has a large spike called a tibial apophysis projecting from it.[14] It is the longer embolus and lacks of bulges on the palpal bulb that distinguish it from Evarcha flagellaris.[12]

The female is similar in shape but larger than the male, with a cephalothorax that measures between 2.5 and 2.6 mm (0.10 and 0.10 in) long and a width between 1.9 and 2 mm (0.07 and 0.08 in). Its carapace is high and convex, mainly yellowish-orange with a scattering of brown hairs on the thorax. The eye field is a lighter yellow with black rings and white scales around the eyes themselves. There are a few bristles at the front of the eye field. The sternum is dark yellow. It has a high clypeus that is covered in fine hairs. The mouthparts are dark yellow like the male.[15]

The female's abdomen is similar in shape to the male.[16] It is an ovoid between 2.4 mm (0.09 in) and 2.5 mm in length and between 1.4 and 1.5 mm (0.06 and 0.06 in) in width. Unlike the male, it is yellowish white on top and white underneath, both with an indistinct pattern of small beige dots forming two lines running down the middle.

Understanding the female's copulatory organs were critical to defining the species.[2] Its external genital structure, or epigyne, is broad with two widely spaced grooves and a wide pocket at the epigastric fold towards the very rear of the spider. The two copulatory openings lead to very wide insemination ducts that are slightly sclerotized and form a loop on their way to the spermathecae or receptacles. These spermathecae are formed of a few chambers. It is the small number of chambers that differentiates the spider from the otherwise similar Evarcha flagellaris.[17]

Behaviour and habitat

Evarcha striolata lives on the ground amongst grasses, particularly grassy tussocks and grass litter. It has been spotted living in forests in the shade of Vachellia xanthophloea and savanna dominated by Vachellia tortilis.[2]

References

Citations

  1. ^ a b World Spider Catalog (2017). "Evarcha striolata Wesolowska& Haddad, 2009". World Spider Catalog. 18.0. Bern: Natural History Museum. Retrieved 10 August 2017.
  2. ^ a b c d e f g Wesołowska & Haddad 2009, p. 35.
  3. ^ Wiśniewski 2020, p. 6.
  4. ^ Wesołowska & Haddad 2009, p. 28.
  5. ^ Maddison, Bodner & Needham 2008, p. 56.
  6. ^ Maddison & Hedin 2003, p. 536.
  7. ^ Prószyński 2017, p. 51.
  8. ^ Prószyński 2018, p. 142.
  9. ^ a b Prószyński 2018, p. 141.
  10. ^ Kropf et al. 2019, p. 445.
  11. ^ Wesołowska & Haddad 2009, p. 95.
  12. ^ a b Haddad & Wesołowska 2011, p. 63.
  13. ^ Haddad & Wesołowska 2011, p. 65.
  14. ^ Wesołowska & Haddad 2009, p. 36.
  15. ^ Wesołowska & Haddad 2013, pp. 178, 197.
  16. ^ Wesołowska & Haddad 2013, p. 178.
  17. ^ Wesołowska & Haddad 2013, pp. 197–198.

Bibliography

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