Thursday, July 14, 2011
Jeffrey Hahn, Assistant Extension Entomologist
Spiders have been very common in and around homes lately. One type that has been particularly conspicuous is fishing spiders. Fishing spiders belong to the family Pisauridae (which also includes nursery web spiders). They are the largest spiders in Minnesota with a body length up to one inch long. Including the legs, they can be as large as several inches across. They are sometimes confused with wolf spiders to which they are very similar in appearance.
Fishing spiders are generally brownish and can have stripes on the body and chevron markings on the abdomen. However, color is not a good method to identify fishing spiders. You can partly do it by size. Another way is to look at the eyes. Like other spiders, fishing spiders have eight eyes which are arranged in two rows of four. As you look straight at the face of a spider, the bottom row (called anterior eyes) is straight or slightly upturned while the top row (called the posterior eyes) is strongly curved. The center two eyes of the top row (called the posterior medial eyes) are little larger than the others.
Fishing spiders are associated with water, such as ponds or lakes, where they feed on a variety of insects, as well as tadpoles and even small fish. They capture prey by sitting on aquatic vegetation or surfaces near water and wait motionless with their legs outstretched for something to swim by. Although they don't construct webs, they do use their silk to attach several leaves together to form a nursery for the egg sacs. Although you typically find fishing spiders near water, one commonly encountered species, Dolomedes tenebrosus, can be commonly found 100 yards or more away from water.
Despite their size, fishing spiders are not aggressive to people and rarely bite (and if they do, it is typically because they are mishandled or feel threatened, like getting accidentally trapped under clothing). Any bites do not hurt any worse than mild bee stings. There is no need to control fishing spiders. If you find one outside, just ignore it. If one accidentally enters your home or other building, just capture it in a jar and release it outside.