Long-jawed Orb Weavers
Tetragnatha spp.
Tetragnathidae -- an Orb Weaver Spider Family
This female Tetragnatha spider at left is closely guarding an egg sac affixed to a cattail leaf and is facing head down. The eggs are covered in layers of soft, white silk which should protect the developing spiderlings from intense sunlight. Photo by Laurie Nessel at the Gilbert Water Ranch, Gilbert, Maricopa County, Arizona, USA. 2009. The name ‘Long-jawed’ refers to the greatly enlarged chelicerae mouthparts of male Tetragnatha, which in some species are as long as the rest of the body! The male, below right, was observed in a web suspended above the flowing waters of Sycamore Creek, Mazatzal Mts., Arizona. May 2010.
These orb-weaving spiders rarely venture far from water, especially in the
Sonoran Desert. Their webs are often suspended above open water supported by
reeds and other emergent vegetation. The plane of their orb is often parallel
to the ground. If disturbed, the spiders immediately leave the web and align
themselves upon a narrow leaf or stem in the vegetation becoming nearly
invisible. While guarding her eggs the female may give up web building - and
feeding. Mosquitoes and non-biting midges are among the prey used. In the name
caption at left ‘spp.’ stands for plural species, i.e. there are a
number of species of Tetragnatha spiders that could be found in
riparian areas of the Sonoran Desert, but identification to exact species
requires a microscope and a considerable degree of expertize.