Fishing from the Dock
I never knew dock spiders were fishing spiders. I’ve seen them hanging around on the dock in the summer but it never dawned on me they used the water like a web to catch insects. I also didn’t know they would eat fish. You learn something new every day.
Dock Spiders
TreeHugger Lloyd Alter grabbed this image of a massive dock spider that appears to be chowing down on a dead fish near his home in Canada. Though dock spiders — also known as fishing spiders — are part of the same genus as fen raft spiders, they’re much more common.
And despite the nerve-racking idea that one could take down a fish this size, they mostly survive on a diet of small insects; they’re also shy enough to run from people, but in the worst case, their bites are about as harmful as a bee sting.
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 fishes 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 Can ada 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 are 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. D. tenebrosus matures in the spring and will subsequently mate. Mature individuals may be found from early May through September. The egg cases 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
Although a large spider such as D. tenebrosus is able to bite humans, it is a shy spider that will run from people. Bites are typically no more severe than a bee or wasp sting. Exceptions do occur for individuals who are sensitive to spider venoms.
Authored by: Steve Jacobs, Sr. Extension Associate