Spotted Fishing Spider

Dolomedes triton
Pisauridae (nursery web weavers) in the order Araneae (spiders)

The first key to identifying spotted fishing spiders is that they live in aquatic habitats and can run across the surface of water. These long-legged, dark-colored water spiders are also distinctive in that the oval abdomen is smaller than the broad cephalothorax (“head”). A pale, whitish-yellow stripe surrounds the dark carapace, and sometimes the abdomen. On top of the dark brown abdomen, three distinctive pairs of minute white spots create a connect-the-dot pattern or run down the middle of the back. The legs are robust and brown, dotted with white hairs. This spider runs quickly.

Length (not including legs): 3/4 inch (females); 1/2 inch (males).
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. The bullfrog is its chief predator.
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 “manna from heaven.”
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 delicious 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. 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.
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