Tetragnatha extensa

Appearance

''T. extensa'' has an elongated, cream-coloured body. Males are smaller than females, at around 9 millimetres body length, compared to 11 mm for females. The four pairs of legs are very long, and are dark yellow. The carapace, which is around 1.8–2.6 mm long and 1.1–1.7 mm wide, is orange or dark yellow.

Distribution

''T. extensa'' has a wide distribution across the Northern Hemisphere. In North America, it is found from Alaska to Newfoundland, and its range extends south to Washington, Colorado and Pennsylvania. The species has a broad ecological range, having been found at the tree line in the Rocky Mountains and in coastal vegetation in Europe. ''T. extensa'' is found throughout the United Kingdom, where it is the commonest species of ''Tetragnatha'', and one of the commonest spiders. The colouring of ''T. extensa'' is quite variable, ranging from creamy-yellow to green. On the underside, there is a thick black central band, with a silvery band on either side.

''T. extensa'' is distinguished from other members of the genus ''Tetragnatha'' by the minute curved tip of the male's conductor , and the form of the female's spermatheca.

Behavior

''Tetragnatha extensa'' is found on low-growing vegetation, usually in damp areas. It feeds on insects, including mosquitos, midges and moths, which it catches in its loosely-constructed web. When alarmed, 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. ''T. extensa'' is able to walk on the surface of water, where it can move faster than on land.Adults are seen between May and September in the United Kingdom, and between May and July in Alaska. There is little courtship, and the male and female lock jaws, possibly to prevent the female from eating the male before mating. The egg sacs are globular and covered with grey tufted silk, resembling a bird dropping, and are pressed against a plant stem. Overwintering occurs in the form of early-instar spiderlings.

Habitat

''Tetragnatha extensa'' is found on low-growing vegetation, usually in damp areas. It feeds on insects, including mosquitos, midges and moths, which it catches in its loosely-constructed web. When alarmed, 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. ''T. extensa'' is able to walk on the surface of water, where it can move faster than on land.

Evolution

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''Tetragnatha extensa'' was first given a binomial by Carl Linnaeus in his ''Systema Naturae'' of 1758, the starting point of zoological nomenclature. In that work, it was included in the genus ''Aranea'' . ''T. extensa'' is a very common, widespread and variable species, and a number of synonyms have been published:

⤷ ''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''
⤷ ''Tetragnatha manitoba'' Chamberlin & Ivie, 1942
⤷ ''Tetragnatha rusticana'' Chickering, 1959
⤷ ''Tetragnatha potanini'' Schenkel, 1963
⤷ ''Tetragnatha maderiana'' Wunderlich, 1987