• Source: 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 it 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. The name Tetragnatha is derived from Greek, tetra- a numerical prefix referring to four and gnatha meaning jaw. Evolution to cursorial behavior occurred long ago in a few different species, the most studied being those found on the Hawaiian islands. 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.
Tetragnatha species are hard to separate from each other without a microscope to scrutinize the genitalia of a mature individual. Hawaiian Tetragnatha appear to distinguish each other via
highly specific chemical compounds in their silk. These chemical differences are especially prominent amongst sympatric and closely-related species. This may constitute a form of chemical species recognition.




Cursorial species found on Hawaiian archipelago


The Tetragnatha spiders found on the Hawaiian archipelago are believed to have no more than three colonization events, two from web building species and one from cursorial species. This is because a species of mainland Tetragnatha spider was found to be more closely related to web building spiders on the Hawaiian islands than the cursorial species. This means that the divergence of web building and cursorial spiders must have occurred off the islands. There have been many events of cursorial evolution in various spider species around the world, including a few Tetragnatha species, although many species have not been thoroughly studied. The factors leading to this change of behavior is not well understood, although study of the Hawaiian Tetragnatha species can lead to some suggestions. Environmental factors, such as landscape and prey diversity play an important role in influencing the structure of webs in web building spiders. This could be a reasonable explanation for the loss of web function and evolving to a cursorial behavior.




Species



As of March 2021 it contains 320 species and ten subspecies, found all over the world, including Greenland:

In synonymy:




See also


List of Tetragnathidae species




References



Media related to Tetragnatha at Wikimedia Commons
Data related to Tetragnatha at Wikispecies

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