Spotted Fishing Spider

Dolomedes triton

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Photo of a spotted fishing spider and several water springtails at the surface of shallow water
Spotted fishing spiders live around ponds, slow-moving streams, swampy areas, and other damp places. So do water springtails, that also live on the surface of quiet water.
Susan Ferber
Other Common Name
Six-Spotted Fishing Spider
Family

Pisauridae (fishing and nursery spiders) in the order Araneae (spiders)

Description

The spotted fishing spider lives in aquatic habitats and can run across the surface of water. This long-legged, dark-colored water spider is also distinctive in that the oval abdomen is smaller than the broad carapace (“head”). A pale, whitish-yellow stripe surrounds the dark carapace and sometimes also the abdomen. Viewed from above, several pairs of small, distinct white spots run down the length of the dark brown abdomen. Apparently, the common name “six-spotted fishing spider” comes from six distinct dark spots on this spider's rarely seen sternum (the underside of the carapace). The legs are robust and brown, dotted with white hairs. This spider runs quickly.

Size

Length (not including legs): ¾ inch (females); ½ inch (males).

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Photo of a spotted fishing spider perched on the water's surface amid floating duckweed plants
Spotted Fishing Spider And Duckweeds
Both the spotted fishing spider and minute duckweed plants are able to float on the surface film of water.

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Image of a fishing spider
Fishing Spider

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Photo of duckweed and a spotted fishing spider on the water surface
Duckweed and Spotted Fishing Spider
Habitat and conservation

Spotted fishing spiders live around ponds, slow-moving streams, swampy areas, and other damp places. They are able to run across the surface of water much like water striders and will dive for prey, including small tadpoles or aquatic insects. The spider encases its body in an air bubble in order to submerge itself, often for several minutes.

Foods

Aquatic insects are at the top of the bill of fare. Tadpoles and tiny fish may also be eaten. Also, when terrestrial or flying insects fall accidentally in the water, fishing spiders can feel the vibrations their struggles create on the surface of the water. They rush across the water to take advantage of this food that drops down from the sky.

image of Spotted Fishing Spider Distribution Map
Distribution in Missouri

Statewide, in appropriate habitats.

Life cycle

As a general rule, spiders in temperate areas hatch from eggs in spring and spend the growing season eating, maturing, mating, and laying eggs. Female spiders are usually much larger than males and sometimes eat the males after mating. Females continue creating egg cases as long as the weather holds out. As temperatures cool in fall, their metabolism slows, and they generally die when it freezes. Egg cases overwinter, and spiderlings hatch in spring.

Human connections

A great many insects live in the water, including young mosquitoes, and anyone who doesn't like mosquitoes should appreciate this spider. Also, this spider is eaten by many species of fish, including bass, sunfish, catfish, and trout, so anglers can appreciate it, too.

Ecosystem connections

In addition to the many fish that eat them, birds, amphibians, and reptiles also catch fishing spiders. The bullfrog is a chief predator. These (and many other spiders) are also stung and collected by certain wasps, which provision their nests with the comatose spiders to provide food for their larvae.