Tetragnatha extensa

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Tetragnatha extensa
Tetragnatha.extensa.web.jpg
T. extensa in its web
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Arachnida
Order: Araneae
Family: Tetragnathidae
Genus: Tetragnatha
Species: T. extensa
Binomial name
Tetragnatha extensa
(Linnaeus, 1758)
Subspecies
  • Tetragnatha extensa brachygnatha Thorell, 1873 — Sweden, Russia
  • Tetragnatha extensa maracandica Charitonov, 1951 — Iran, Russia, Central Asia
  • Tetragnatha extensa pulchra Kulczynski, 1891 — Hungary

Tetragnatha extensa is a species of spider found across the Northern Hemisphere. It has an elongate body, up to 11 mm (0.43 in) long, and adopts a straight line posture when alarmed. It lives on low vegetation in damp areas, and feeds on flying insects which it catches in its web.

Description[edit]

T. extensa has an elongated, cream-coloured body.[1] Males are smaller than females, at around 9 millimetres (0.35 in) body length, compared to 11 mm (0.43 in) for females.[2] The four pairs of legs are very long,[1] and are dark yellow.[3] The carapace, which is around 1.8–2.6 mm long and 1.1–1.7 mm wide, is orange or dark yellow.

The colouring of T. extensa is quite variable,[4] ranging from creamy-yellow to green.[2] On the underside, there is a thick black central band, with a silvery band on either side.[3]

T. extensa is distinguished from other members of the genus Tetragnatha by the minute curved tip of the male's conductor (part of the pedipalp), and the form of the female's spermatheca.[3]

Distribution[edit]

T. extensa has a wide distribution across the Northern Hemisphere (Holarctic).

In North America, it is found from Alaska to Newfoundland, and its range extends south to Washington, Colorado and Pennsylvania.[3] The species has a broad ecological range, having been found at the tree line in the Rocky Mountains.

It is found in coastal vegetation in Europe.[3] T. extensa is found throughout the United Kingdom,[2] where it is the commonest species of Tetragnatha,[4] and one of the commonest spiders.[1] It is also found in Madeira.

T. extensa in its defensive posture

Ecology and behaviour[edit]

Tetragnatha extensa is found on low-growing vegetation, usually in damp areas.[1] It feeds on insects, including mosquitos, midges and moths, which it catches in its loosely constructed web.[1] When alarmed,[2] it will sit along a plant stem, a blade of grass or the central vein of a leaf, with its four front legs pointing forwards, and its four back legs pointing backwards for camouflage.[1] T. extensa is able to walk on the surface of water, where it can move faster than on land.[5]

Life cycle[edit]

Adults are seen between May and September in the United Kingdom,[2] and between May and July in Alaska.[3] There is little courtship, and the male and female lock jaws, possibly to prevent the female from eating the male before mating.[5] The egg sacs are globular and covered with grey tufted silk,[3] resembling a bird dropping,[5] and are pressed against a plant stem.[3] Overwintering occurs in the form of early-instar spiderlings.[3]

Taxonomic history[edit]

Tetragnatha extensa was first given a binomial by Carl Linnaeus in his Systema Naturae of 1758, the starting point of zoological nomenclature.[6] In that work, it was included in the genus Aranea (now Araneus). T. extensa is a very common, widespread and variable species, and a number of synonyms have been published:[6]

  • Aranea extensa Linnaeus, 1758
  • Aranea solandri Scopoli, 1763
  • Aranea mouffeti Scopoli, 1763
  • Tetragnatha rubra Risso, 1826
  • Tetragnatha gibba C. L. Koch, 1837
  • Tetragnatha chrysochlora Walckenaer, 1841
  • Tetragnatha arundinis Bremi-Wolff, 1849
  • Tetragnatha fluviatilis Keyserling, 1865
  • Tetragnatha nowickii L. Koch, 1870
  • Tetragnatha groenlandica Thorell, 1872
  • Tetragnatha solandri (Scopoli, 1763)
  • Tetragnatha manitoba Chamberlin & Ivie, 1942
  • Tetragnatha rusticana Chickering, 1959
  • Tetragnatha potanini Schenkel, 1963
  • Tetragnatha maderiana Wunderlich, 1987

References[edit]

  1. ^ a b c d e f "Tetragnatha extensa – a long-jawed spider". Natural England. Retrieved September 22, 2010. 
  2. ^ a b c d e "Tetragnatha extensa". Spiders. UK Safari. Retrieved September 22, 2010. 
  3. ^ a b c d e f g h i Charles D. Dondale & James H. Redner (2003). "Tetragna extensa (Linnaeus)". The Orb-weaving Spiders of Canada and Alaska: Araneae: Uloboridae, Tetragnathidae, Araneidae, Theridiosomatidae. Part 23 of Insects and Arachnids of Canada. NRC Research Press. pp. 71–73. ISBN 978-0-660-18898-0. 
  4. ^ a b "Tetragnatha extensa". Nick's Spiders of Britain and Europe. Retrieved September 22, 2010. 
  5. ^ a b c "Long-jawed orb weaver, Tetragnatha extensa". Science & Nature: Animals. BBC. 
  6. ^ a b Norman I. Platnick (June 7, 2010). "Tetragnathidae". The World Spider Catalog, Version 11.0. American Museum of Natural History. 

External links[edit]