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.
Distribution Species in this genus are found worldwide, including Greenland.
Habitat and ecology
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.
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.
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.
Morphology
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.
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.
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.
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.
Species distinction 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.
Name The name Tetragnatha is derived from Greek, tetra- a numerical prefix referring to four and gnatha meaning jaw.
Species
, this genus includes 309 species and nine subspecies.
Species with articles on Wikipedia:
Tetragnatha armata Karsch, 1892 – Sri Lanka Tetragnatha bogotensis Keyserling, 1865 – Mexico to Paraguay, Caribbean. Introduced to Spain, Italy (Sardinia), Africa, Seychelles, Yemen, India, Nepal, Bangladesh, China Tetragnatha caffra (Strand, 1909) – South Africa Tetragnatha caudata Emerton, 1884 – North, Central America, Cuba, Jamaica, Uruguay, Argentina Tetragnatha ceylonica O. Pickard-Cambridge, 1869 – Mozambique, South Africa, Seychelles, India, Thailand, Philippines, New Guinea, Japan (Ryukyu Is.) Tetragnatha demissa L. Koch, 1872 – Australia. Introduced to Cyprus, Tanzania, South Africa, Seychelles, Tonga Tetragnatha determinata Karsch, 1892 – Sri Lanka Tetragnatha elongata Walckenaer, 1841 – Canada to Argentina, Caribbean 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 flavida Urquhart, 1891 – New Zealand Tetragnatha foveata Karsch, 1892 – Sri Lanka, Laccadive Is. Maldive Is. Tetragnatha geniculata Karsch, 1892 – India, Sri Lanka, China, Myanmar, Thailand, Vietnam Tetragnatha guatemalensis O. Pickard-Cambridge, 1889 – North and Central America, Cuba, Jamaica, Brazil, Paraguay Tetragnatha hasselti Thorell, 1890 – India to China, Indonesia (Sulawesi) 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 laboriosa Hentz, 1850 – Alaska to Chile, Argentina, Falkland Is. Tetragnatha mandibulata Walckenaer, 1841 – Central America, Caribbean, Colombia, Guyana, Brazil, West Africa, India to Philippines, Australia Tetragnatha montana Simon, 1874 – Europe, Turkey, Caucasus, Russia (Europe to Far East), Kazakhstan, Iran, Central Asia Tetragnatha multipunctata Urquhart, 1891 – New Zealand Tetragnatha nigricans Dalmas, 1917 – New Zealand 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 planata Karsch, 1892 – Sri Lanka Tetragnatha praedonia L. Koch, 1878 – Russia (Far East), Korea, Japan, China, Taiwan, Laos Tetragnatha squamata Karsch, 1879 – India, China, Taiwan, Russia (Far East), Korea, Japan Tetragnatha straminea Emerton, 1884 – Canada, United States, Cuba Tetragnatha subsquamata Okuma, 1985 – Tanzania, South Africa Tetragnatha taylori O. Pickard-Cambridge, 1891 – South Africa Tetragnatha tenera Thorell, 1881 – Sri Lanka, Australia (Queensland) Tetragnatha torrensis Schmidt & Piepho, 1994 – Cape Verde Tetragnatha unicornis Tullgren, 1910 – Tanzania, Botswana, South Africa Tetragnatha vermiformis Emerton, 1884 – Temperate and tropical Asia. Introduced to North and Central America, Brazil, South Africa Tetragnatha versicolor Walckenaer, 1841 – North, Central America, Cuba Tetragnatha virescens Okuma, 1979 – Bangladesh, Sri Lanka to Indonesia, Philippines Tetragnatha viridis Walckenaer, 1841 – Canada, United States Tetragnatha yesoensis Saito, 1934 – Russia (Far East), China, Korea, Japan
Tetragnatha acuta Gillespie, 1992 – Hawaii Tetragnatha aenea Cantor, 1842 – China Tetragnatha aetherea (Simon, 1895) – Venezuela Tetragnatha albida Gillespie, 1994 – Hawaii Tetragnatha amazonica Castanheira, Baptista & Oliveira, 2022 – Venezuela Tetragnatha amoena Okuma, 1987 – New Guinea Tetragnatha anamitica Walckenaer, 1841 – Vietnam Tetragnatha andamanensis Tikader, 1977 – India (Andaman Is.), Bangladesh Tetragnatha andonea Lawrence, 1927 – Namibia Tetragnatha angolaensis Okuma & Dippenaar-Schoeman, 1988 – Angola Tetragnatha anguilla Thorell, 1877 – Indonesia (Java, Sulawesi), New Guinea, Australia Tetragnatha angulata Hogg, 1914 – Australia (Western Australia) Tetragnatha anuenue Gillespie, 2002 – Hawaii Tetragnatha argentinensis Mello-Leitão, 1931 – Brazil, Uruguay, Argentina Tetragnatha armata Karsch, 1892 – Sri Lanka Tetragnatha atriceps Banks, 1898 – Mexico Tetragnatha atristernis Strand, 1913 – Central Africa Tetragnatha baculiferens Hingston, 1927 – Myanmar Tetragnatha beccarii Caporiacco, 1947 – Guyana Tetragnatha bengalensis Walckenaer, 1841 – India Tetragnatha bicolor White, 1841 – Australia (Tasmania) Tetragnatha bifurcata Li & Liu, 2022 – China Tetragnatha bimaculata Li & Liu, 2022 – China Tetragnatha biseriata Thorell, 1881 – New Guinea (Indonesia, Papua New Guinea), Australia (Queensland) Tetragnatha bituberculata L. Koch, 1867 – Japan, New Guinea, Australia Tetragnatha boeleni Chrysanthus, 1975 – New Guinea Tetragnatha bogotensis Keyserling, 1865 – Mexico to Paraguay, Caribbean. Introduced to Spain, Italy (Sardinia), Africa, Seychelles, Yemen, India, Nepal, Bangladesh, China Tetragnatha boninensis Okuma, 1981 – Japan Tetragnatha brachychelis Caporiacco, 1947 – Tanzania, Kenya Tetragnatha branda Levi, 1981 – United States Tetragnatha brevignatha Gillespie, 1992 – Hawaii Tetragnatha bryantae Roewer, 1951 – Puerto Rico Tetragnatha caffra (Strand, 1909) – South Africa Tetragnatha cambridgei Roewer, 1942 – Mexico, Central America, Puerto Rico Tetragnatha caudata Emerton, 1884 – North, Central America, Cuba, Jamaica, Uruguay, Argentina Tetragnatha caudicula (Karsch, 1879) – Russia (Far East), China, Korea, Taiwan, Japan, Mexico Tetragnatha caudifera (Keyserling, 1887) – Australia (New South Wales) Tetragnatha cavaleriei Schenkel, 1963 – China Tetragnatha cephalothoracis Strand, 1906 – Ethiopia Tetragnatha ceylonica O. Pickard-Cambridge, 1869 – Mozambique, South Africa, Seychelles, India, Thailand, Philippines, New Guinea, Japan (Ryukyu Is.) Tetragnatha chauliodus (Thorell, 1890) – China, Japan, Myanmar to Papua New Guinea, Brazil (introduced?) Tetragnatha cheni Zhu, Song & Zhang, 2003 – China Tetragnatha chinensis (Chamberlin, 1924) – China Tetragnatha chiyokoae Castanheira & Baptista, 2020 – China, Taiwan, Japan Tetragnatha cladognatha Bertkau, 1880 – Brazil, Argentina Tetragnatha clavigera Simon, 1887 – Sierra Leone, Ivory Coast, DR Congo Tetragnatha cochinensis Gravely, 1921 – India Tetragnatha coelestis Pocock, 1901 – India Tetragnatha cognata O. Pickard-Cambridge, 1889 – Guatemala to Panama Tetragnatha conica Grube, 1861 – Russia (Far East) Tetragnatha corsica Simon, 1929 – France (Corsica) Tetragnatha crassichelata Chrysanthus, 1975 – New Guinea Tetragnatha cristata Castanheira, Baptista & Oliveira, 2022 – Brazil, Argentina Tetragnatha cuneiventris Simon, 1900 – Hawaii Tetragnatha cylindracea (Keyserling, 1887) – Australia (Queensland, New South Wales) Tetragnatha cylindrica Walckenaer, 1841 – New Guinea, Australia, Fiji Tetragnatha cylindriformis Lawrence, 1952 – Congo Tetragnatha dearmata Thorell, 1873 – North America, Europe, Caucasus, Russia (Europe to Far East) Tetragnatha delumbis Thorell, 1891 – India (Nicobar Is.) Tetragnatha demissa L. Koch, 1872 – Australia. Introduced to Cyprus, Tanzania, South Africa, Seychelles, Tonga