The spider family Tetragnathidae (longjawed orb weavers) includes 966 described species (Platnick 2014), with around three dozen of these occurring in North America north of Mexico (Levi 2005; Platnick 2014).
Tetragnathids typically have long, thin bodies and legs, with the first pair of legs the longest and the third pair the shortest. The cheliceral bases and fangs are elongated. The male's palps are long and thin as well. The front two pairs of legs are often stretched out in front of the body, especially when the spider is at rest. During mating, the male and female tightly interlock their large jaws, but the long palps of the male are able to reach the female's reproductive opening even in this position. (Bradley 2013) Like most spiders, tetragnathids have eight eyes.
Most tetragnthids spin orb webs to capture prey. These webs are often oriented horizontally with an open hub. Many species build their webs near water or in vegetation above it, capturing emerging insects such as mosquitos. One exception is Leucauge, which often build webs at an oblique angle to the horizontal, often well away from water. Their conspicuous webs and silvery and green colors often make these spiders easy to notice. Nephila constructs vertical, bright yellow webs. Meta builds in dark places such as in caves or wells. Pachygnatha builds only in very early instars, in later stages becoming wandering hunters. (Levi 2005; Bradley 2013)
Tetragnathidae have been transferred in and out of the old families Epeiridae and Argiopidae, as well as the present-day Araneidae. Levi (1980, 1981) revised and illustrated the North American species (subsequently, Marusik and Koponen  determined that the North American Meta "menardi" is distinct from the European species and gave it a new name, "M. americana" but Dondale  found an earlier name, with priority, for the American Meta, M. ovalis).
The orb weaving spider family Tetragnathidae includes about 1000 described species in 51 genera (Platnick, 2009). The family is most diverse in the tropical regions and many species still remain unknown to science. Many tetragnathids are associated with some of the world's most important and fragile ecosystems, wetlands and river ecosystems, often building their orb webs very close to the water surface. Although many species live in relatively humid conditions, there are also others that thrive in dry climates. A good number of species are known from caves, such as many of the members of the genus Meta. Species in the genus Tetragnatha provide a striking example of dispersion abilities and ecological plasticity. With more than 340 described species and a distribution range that spans from the Arctic to the most remote oceanic islands Tetragnatha is one of the champions of the animal kingdom.
Tetragnathidae Menge, 1866
Tetragnathidae Menge, 1866
Most tetragnathid males have conspicuously enlarged chelicerae, often armored with numerous teeth. Some of these teeth, along with specialized cheliceral apophyses, play an important role during courtship and copulation as they are involved in a behavior known as cheliceral clasp (Bristowe, 1958; Eberhard and Huber, 1998). Other characters common to most tetragnathids are the close association of the embolus and conductor in the male palp, the presence of conspicuous trichobothria on the fourth leg femur and juxtaposed lateral eyes. Nevertheless, morphological features vary considerably within the family and there are several species that differ from the typical tetragnathid morphology. Females of the majority of tetragnathid genera have entelegyne genitalia, but the members of the subfamily Tetragnathinae provide a remarkable exception: all tetragnathines are secondarily haplogyne.
Tetragnatha javana. Left: male chelicerae frontal. Right: female chelicerae, frontal. Note the numerous teeth and cheliceral apophyses on the male chelicerae. Images © 2008 Dimitar Dimitrov
Most tetragnathids build orb webs of similar architecture, often with open hubs. Pachygnatha species have abandoned web building as a hunting strategy and actively search for food wandering around.
Evolution and Systematics
Discussion of Phylogenetic Relationships
The first phylogenetic analysis of tetragnathids was that of Levi (1980) which did not recover Tetragnathidae monophyly, but his taxon and character sample was very limited. The first to demonstrate the monophyly of Tetragnathidae using numerical cladistic methods was Coddington (1990). He was also the first to suggest that tetragnathids are more closely related to other araneoid lineages than Araneidae. All subsequent cladistic analyses that included tetragnathid representatives have recovered the monophyly of the family. Earlier phylogenetic analyses of tetragnathids and their relatives relied heavily on morphological data and included a smaller fraction of behavioral characters (Coddington, 1990; Hormiga et al., 1995; Griswold et al., 1998). All these earlier studies included Nephila and its relatives in the tetragnathid subfamily Nephilinae, together with the genus Phonognatha. Kuntner (2005) elevated the subfamily Nephilinae to family rank and suggested that Deliochus and Phonognatha may not belong in Tetragnathidae. Later on Kuntner et al. (2008) formally transferred Deliochus and Phonognatha to the family Araneidae.
Recent and ongoing work on tetragnathids has further advanced our knowledge about the phylogenetic structure of this family. Álvarez-Padilla (2007) and Dimitrov and Hormiga (2009) have used extensive morphological and behavioral data to study tetragnathid phylogeny. More recently, Álvarez-Padilla et al. (2009) have added multigene DNA sequence data to the morphological and behavioral evidence. We present here the results of their study as the most current phylogenetic classification for Tetragnathidae. Álvarez-Padilla et al.'s (2009) study confirmed that Nephila and its relatives do not belong into Tetragnathidae (as it had been proposed by some earlier classifications, such as Eugene Simon's), but their exact phylogenetic placement remains unclear.
Molecular Biology and Genetics
Statistics of barcoding coverage
Specimens with Sequences:2971
Specimens with Barcodes:2858
Species With Barcodes:122
Long-jawed orb weaver
The spiders are orb web weavers, weaving small orb webs with an open hub and few, wide-set radii and spirals. The webs have no signal line and no retreat. Some species are often found in long vegetation near water.
The categorization into subfamilies follows Joel Hallan's Biology Catalog.
- Azilia Keyserling, 1881
- Dianleucauge Song & Zhu, 1994
- Eryciniolia Strand, 1912
- Leucauge White, 1841
- Mecynometa Simon, 1894
- Memoratrix Petrunkevitch, 1942 † (fossil, oligocene)
- Mesida Kulczyn'ski, 1911
- Nanometa Simon, 1908
- Okileucauge Tanikawa, 2001
- Opadometa Archer, 1951
- Pickardinella Archer, 1951
- Tylorida Simon, 1894
- Atelidea Simon, 1895
- Atimiosa Simon, 1895
- Chrysometa Simon, 1894
- Diphya Nicolet, 1849
- Dolichognatha O. P.-Cambridge, 1869
- Homalometa Simon, 1897
- Meta C. L. Koch, 1836
- Metabus O. P.-Cambridge, 1899
- Metargyra F. O. P.-Cambridge, 1903
- Metellina Chamberlin & Ivie, 1941
- Metleucauge Levi, 1980
- Nanningia Zhu, Kim & Song, 1997
- Parameta Simon, 1895
- Prolochus Thorell, 1895
- Schenkeliella Strand, 1934
- Zygiometella Wunderlich, 1995
- Tetragnathinae Menge, 1866
- Agriognatha O. P.-Cambridge, 1896
- Antillognatha Bryant, 1945
- Cyrtognatha Keyserling, 1881
- Doryonychus Simon, 1900
- Dyschiriognatha Simon, 1893
- Glenognatha Simon, 1887
- Hispanognatha Bryant, 1945
- Mimicosa Petrunkevitch, 1925
- Mitoscelis Thorell, 1890
- Pachygnatha Sundevall, 1823
- Prionolaema Simon, 1894
- Tetragnatha Latreille, 1804
- Alcimosphenus Simon, 1895 (formerly Araneidae)
- Deliochus Simon, 1894 (formerly Nephilinae)
- Eometa Petrunkevitch, 1958 † (fossil)
- Guizygiella Zhu, Kim & Song, 1997
- Leucognatha Wunderlich, 1992
- Macryphantes Selden, 1990 † (fossil, limestone)
- Menosira Chikuni, 1955
- Neoprolochus Reimoser, 1927
- Orsinome Thorell, 1890
- Palaeometa Petrunkevitch, 1922 † (fossil)
- Palaeopachygnatha Petrunkevitch, 1922 † (fossil)
- Parazilia Lessert, 1938
- Pholcipes Schmidt & Krause, 1993
- Phonognatha Simon, 1894 (formerly Nephilinae)
- Priscometa Petrunkevitch, 1958 † (fossil)
- Sancus Tullgren, 1910
- Sternospina Schmidt & Krause, 1993
- Theridiometa Petrunkevitch, 1942 † (fossil, oligocene)
- Timonoe Thorell, 1898
- Wolongia Zhu, Kim & Song, 1997
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