Tetragnatha extensa
| Tetragnatha extensa | |
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_Tetragnatha_extensa_on_Philadelphus_coronarius.jpg)
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| T. extensa on Philadelphus coronarius | |
Scientific classification 
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| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Subphylum: | Chelicerata |
| Class: | Arachnida |
| Order: | Araneae |
| Infraorder: | Araneomorphae |
| Family: | Tetragnathidae |
| Genus: | Tetragnatha |
| Species: | T. extensa
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| Binomial name | |
| Tetragnatha extensa | |
| Subspecies | |
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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.
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]- ^ a b c d e f "Tetragnatha extensa – a long-jawed spider". Natural England. Retrieved September 22, 2010.
- ^ a b c d e "Tetragnatha extensa". Spiders. UK Safari. Retrieved September 22, 2010.
- ^ 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.
- ^ a b "Tetragnatha extensa". Nick's Spiders of Britain and Europe. Retrieved September 22, 2010.
- ^ a b c "Long-jawed orb weaver, Tetragnatha extensa". Science & Nature: Animals. BBC.
- ^ a b Norman I. Platnick (June 7, 2010). "Tetragnathidae". The World Spider Catalog, Version 11.0. American Museum of Natural History.
External links
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Media related to Tetragnatha extensa at Wikimedia Commons
