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Wednesday, 17 July 2019

17-7-2019 ALBUFERA, VALENCIA - STRETCH SPIDER (Genus Tetragnatha)


Tetragnatha is a genus of long-jawed orb-weavers found all over the world. It was first described by Pierre André Latreille in 1804, and contains hundreds of species. Most occur in the tropics and subtropics, and many can run over water. They are commonly called stretch spiders in reference to their elongated body form and their ability to hide on blades of grass or similar elongated substrates by stretching their front legs forward and the others behind them.

Species in this genus are found worldwide, including Greenland.

Tetragnatha species occupy the tall herb and tree layer. They construct orb webs, usually in vegetation near or above streams and ponds. Several studies have reported that they build their webs near slow-flowing streams in sunlit areas. Without access to a humid habitat, these spiders suffer from dehydration. The webs are short-lived, being taken down and digested daily or even more frequently. Webs are usually horizontally inclined and consist of an open hub with 30 to 40 viscid spirals. The spider hangs underneath the central hub of the web with its long front legs directed forward.

These spiders are capable of walking over water surfaces at a very fast pace, with legs I and II moving alternately in a diagonal rhythm while legs III and IV are dragged behind. When at rest on vegetation, the body is pressed against the substrate with the long front legs stretched forward.

One of the biggest and most common species is T. extensa, which has a holarctic distribution. It can be found near lakes, river banks or swamps. Large numbers of individuals can often be found in reeds, tall grass, and around minor trees and shrubs.