Pisauridae—Nursery Web Spiders

Dolomedes tenebrosus

Fishing spiders are similar to the larger wolf spiders in size, shape, and coloration. Species in the genus Dolomedes are called fishing spiders because most live near water and have been reported to catch small fish and aquatic insects from the water as they walk on the surface. The species Dolomedes tenebrosus is more frequently associated with wooded areas (it would be more accurately classified as a tree-dwelling spider) and is a common household invader in these locations. It occurs from New England and Canada south to Florida and Texas.

Description

D. tenebrosus is a fairly large spider. The females are 15 to 26 millimeters in length; males are 7 to 13 millimeters. Both sexes are brownish gray in color with black and lighter brown markings. The legs of both male and female are banded with alternating brown/black, scalloped annulations on the femora and reddish-brown/black annulations on the tibia. A closely related species, D. scriptus, is similar but has white “W" markings on the posterior portion of the abdomen.

Life History

Dolomedes tenebrosus is frequently found far away from water, usually in wooded settings. They hibernate as immature adults (penultimate instar) under stones or loose bark, in tree cavities, and in human-made structures and mature in the spring. Mature individuals may be found from early May through September. The egg sacs are deposited in June and are carried around by the females until the spiderlings are ready to hatch. Young spiderlings may be found from July through September. The young are guarded by the female in a nursery web and may number 1,000 or more.

Medical Importance

Fishing spiders are quite shy and generally run from humans at the slightest movement. Bites are typically no more severe than a bee or wasp sting. Exceptions do occur in individuals who are sensitive to spider venoms.

Reference

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