Walking on water: fishing spiders

On a calm pond or an isolated pool near the river, you might spy what first appears to be a water strider, water boatman of perhaps an unlucky insect which fell in the water. A closer inspection, however, shows what appears to be a spider on, not in, the water. This spider seems to have no difficulty in supporting itself on the water, as if the water’s surface were a plate of glass. Behold the fishing spider getting in a last water walk before the cold is here to stay.

Fishing spiders are members of the genus Dolomedes, and usually live near water. Their ability to walk on the water’s surface is due to spiders’ ability to utilize the surface tension of the water as water striders and other surface dwelling aquatic insects do. Fishing spiders are wandering spiders. They do not build a web to trap food. Instead, they run on the water’s surface, or on a nearby shoreline chasing insects, or even small fish. They can be frequently found on rocks along the shore resting or lying in wait for nearby prey.

During mating season, the female spider carries an egg sac underneath her body, which may contain over 1000 eggs. The male is frequently killed by the female after mating. Just before the eggs hatch, the female attaches the egg sac to a fixed object and builds a nursery web around the eggs. She then stands watch nearby as the eggs hatch and the young spiderlets grow.