Stretch spiders (Tetragnatha sp.)

Stretch spiders (Tetragnatha sp. (Latreille, 1804))

Scientific name: Tetragnatha sp. (Latreille, 1804)
Common name: Stretch spiders
Other names: Long-jawed Orb Weavers
French name: Tétragnathes
Order: Araneae
Family: Tetragnathidae
Size:
Biotope: European species are mainly observed near water, in bogs or damp forests.
Web: Orbicular web with a central hole.
Observation period:
Geographic area: Worldwide. The largest number of species is found in tropical and subtropical regions.

Stretch spiders show an elongated and thin body. They are used to hiding along stems, leaves and branches by stretching their pair of legs forwards and backwards.
The fore legs are longer than the other ones. The chelicerae are long and extend between the front legs.
About 336 species are listed in this genus worldwide with 14 in Europe and 10 in France. They are Tetragnatha dearmata (Thorell, 1873), Tetragnatha extensa (Linnaeus, 1758), Tetragnatha intermedia (Kulczynski, 1891), Tetragnatha isidis (Simon, 1880), Tetragnatha montana (Simon, 1874), Tetragnatha nigrita (Lendl, 1886), Tetragnatha nitens (Audouin, 1826), Tetragnatha obtusa (C. L. Koch, 1837), Tetragnatha pinicola (L. Koch, 1870) and Tetragnatha striata (L. Koch, 1862).
Telling species apart with only field pictures is almost always impossible.
Two members of the above list show a sternum marked with a yellow median stripe. This is Tetragnatha extensa and Tetragnatha pinicola. Tetragnatha extensa is the commonest species. You can use body size for identification as Tetragnatha pinicola's body does not exceed 6 mm in length while Tetragnatha extensa's body can reach 12 mm.
The other species in the list show a uniform dark sternum, almost black or dark brown. Tetragnatha montana is the most common species in the group.

Stretch spiders (Tetragnatha sp.) - Yvelines, France - May 29th 2008

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