Tetragnatha is a genus of long-jawed orb-weavers found all over the world. It was first described by Pierre André Latreille in 1804,[1] 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.
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.[3]
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.[3]
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.[4] Large numbers of individuals can often be found in reeds, tall grass, and around minor trees and shrubs.
Cursorial species found on Hawaiian archipelago
Evolution to cursorial behavior occurred long ago in a few different species, the most studied being those found on the Hawaiian islands.[5]
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.[5] 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,[6] 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[7] and prey diversity play an important role in influencing the structure of webs in web building spiders.[8] This could be a reasonable explanation for the loss of web function and evolving to a cursorial behavior.
Morphology
Eye arrangement of Tetragnatha
The general coloration ranges from fawn to dull brown or grey with silvery markings. The carapace is longer than wide, and the sternum is longer than wide with a pointed posterior end. Eight eyes are arranged in two rows, with lateral eyes slightly apart.[3]
The chelicerae are notably variable, being long and well developed, featuring rows of large teeth and strong projecting spurs that are markedly elongated in males. The endites are parallel. The legs bear three claws and are long and slender, with or without spines.[3]
The abdomen is elongated and cylindrical in some species, extending posteriorly beyond the spinnerets. The spinnerets are unmodified, with anterior and posterior pairs similar in size.[3]
In females, the epigyne has genital openings located at the posterior end of the procurved epigastric furrow, with the genital plate not sclerotized. Males possess a separate and movable paracymbium with a coiled embolus and conductor at the distal tip.[3]
Species distinction
Tetragnatha species are hard to separate from each other without a microscope to scrutinize the genitalia of a mature individual.[9] 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.[10]
Name
The name Tetragnatha is derived from Greek, tetra- a numerical prefix referring to four and gnatha meaning jaw.
Tetragnatha extensa (Linnaeus, 1758) – North America, Greenland, Europe, Turkey, Caucasus, Russia (Europe to Far East), Iraq, Iran, Kazakhstan, Central Asia, China, Korea, Japan (type species)
Tetragnatha isidis (Simon, 1880) – Southern Europe, Libya, Egypt, Sudan, Uganda, South Africa, Iran, India
Tetragnatha jaculator Tullgren, 1910 – Africa to China and India, New Guinea (Indonesia, Papua New Guinea). Introduced to the Caribbean and South America
Tetragnatha keyserlingi Simon, 1890 – Central America, Caribbean, Brazil, Africa, Korea, China, India to Philippines, New Hebrides, Polynesia
Tetragnatha nitens (Audouin, 1826) – Tropical and subtropical Asia. Introduced to Americas, Macaronesia, Mediterranean, St. Helena, South Africa, Madagascar, Pacific Is. New Zealand
Tetragnatha pallescens F. O. Pickard-Cambridge, 1903 – North, Central America, Caribbean
Tetragnatha elyunquensis Petrunkevitch, 1930 – Jamaica, Puerto Rico
Tetragnatha esakii Okuma, 1988 – Taiwan
Tetragnatha eumorpha Okuma, 1987 – New Guinea
Tetragnatha eurychasma Gillespie, 1992 – Hawaii
Tetragnatha exigua Chickering, 1957 – Jamaica
Tetragnatha exquista Saito, 1933 – Japan
Tetragnatha extensa (Linnaeus, 1758) – North America, Greenland, Europe, Turkey, Caucasus, Russia (Europe to Far East), Iraq, Iran, Kazakhstan, Central Asia, China, Korea, Japan (type species)
T. e. brachygnatha Thorell, 1873 – Sweden, Russia (Kamchatka)
T. e. maracandica Charitonov, 1951 – Iran, Central Asia
T. e. pulchra Kulczyński, 1891 – Hungary
Tetragnatha fallax Thorell, 1881 – Indonesia
Tetragnatha farri Chickering, 1962 – Jamaica
Tetragnatha filiciphilia Gillespie, 1992 – Hawaii
Tetragnatha filipes Schenkel, 1936 – China
Tetragnatha filum Simon, 1907 – Congo, Equatorial Guinea (Bioko), São Tomé and Príncipe
Tetragnatha flagellans van Hasselt, 1882 – Indonesia (Sumatra)
Tetragnatha jaculator Tullgren, 1910 – Africa to China and India, New Guinea (Indonesia, Papua New Guinea). Introduced to the Caribbean and South America
Tetragnatha javana (Thorell, 1890) – Africa, Asia
Tetragnatha jejuna (Thorell, 1897) – Myanmar
Tetragnatha josephi Okuma, 1988 – India, Malaysia, Singapore
Tetragnatha jubensis Pavesi, 1895 – Ethiopia
Tetragnatha kamakou Gillespie, 1992 – Hawaii
Tetragnatha kapua Gillespie, 2003 – Marquesas Is.
Tetragnatha kauaiensis Simon, 1900 – Hawaii
Tetragnatha kea Gillespie, 1994 – Hawaii
Tetragnatha keyserlingi Simon, 1890 – Central America, Caribbean, Brazil, Africa, Korea, China, India to Philippines, New Hebrides, Polynesia
Tetragnatha nigrita Lendl, 1886 – Europe, Caucasus, Russia (Europe to Far East), Kazakhstan, Iran, Central Asia, China, Japan
Tetragnatha niokolona Roewer, 1961 – Senegal
Tetragnatha nitens (Audouin, 1826) – Tropical and subtropical Asia. Introduced to Americas, Macaronesia, Mediterranean, St. Helena, South Africa, Madagascar, Pacific Is. New Zealand
Tetragnatha nitidiuscula Simon, 1907 – West Africa
↑ 3.03.13.23.33.43.5Dippenaar-Schoeman, A.S.; Haddad, C.R.; Foord, S.H.; Lotz, L.N. (2023). The Tetragnathidae of South Africa. Version 2. South African National Survey of Arachnida Photo Identification Guide. p. 33. doi:10.5281/zenodo.7513261. This article incorporates text available under the CC BY 4.0 license.
↑Hänggi, Ambros; Stöckli, Edi; Nentwig, Wolfgang (1995). Lebensräume Mitteleuropäischer Spinnen. Miscellanea Faunistica Helvetiae – Centre suisse de cartographie de la faune, Neuchatel. ISBN2-88414-008-5.
Tetragnatha sp.
resting on Impatiens
mating
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