Pest Library

Characteristics

The six-spotted fishing spider (Dolomedes triton) is a large aquatic spider from the family Pisauridae. This arachnid has six black spots under their sternum, hence the name. The color of their body is grey to brown with two white colored stripes on each side of their cephalothorax. Their abdomen is usually dark brown in color with series of light colored spots. The six-spotted fishing spider has eight eyes which are almost equal in size. Similar to a lot of other species, their males are smaller than the females. The body of the female is about 1/2 to 4/5 inch in length, with the legs excluded. While the length of a male six-spotted fishing spider is only 31/100 to 9/20 inch, without the legs.

Habitat

The six-spotted fishing spider can be found in areas where plants are present, in still water, in streams, even in trees. Although they do not spin webs, like normal spiders do, they can move around their habitats to catch their prey.

Behavior

This amazing spider is very agile, both in land and in water, but its ability in water is what makes this spider extra special. This fishing spider can walk on water, move on, go underneath, or go on the top of the water without drowning.

Abilities of the fishing spiders are:
• Walk and run on surface of water
• Submerge underwater with the use of a leaf or a plant
• Use their legs as oars as they row
• Trap a bubble of air on their legs to allow breathing underwater as they dive
• Let the wind push them so they can glide on water

The fishing spider has its “book lungs” to thank for. Their rotating layers of air pockets in its body is what makes the fishing spider able to submerge, dive, glide, run, row, and walk on water. This spider also has a body that is concealed with short-repellent hairs that work when the spider submerges underwater. They will be able to submerge underwater for at least thirty minutes because of their somewhat “air tank” ability. However, this ability can also make the spider buoyant that it will need to grab on to something from underneath to stop itself from floating.

Food

This fishing spider like insects and they have numerous options because of their advantages. They can either find food on land, and on the water surface and even below. Their common meals are terrestrial insects that fell off in the water, however, they can also consume other types of aquatic insects. Larger preys also fall victim to the six-spotted fishing spider as they can eat small fish, frogs and newts.

Life Cycle

When a young male spider searches for a female to mate, he needs to be especially attentive since the female is twice her size and may cannibalize him as she needs protein to produce eggs. If the female is receptive to him, he may be able to stop her from eating him. However, it is common for this female spider to eat her mate to raise the probability of having her eggs to hatch on time.

To protect her eggs, she will make a ball-shaped egg sac that she will bring in her jaws to a secure location until before the spiderlings are all set to hatch. In order to prepare for the spiderlings, she will create a nursery web, then place the egg sac inside while guarding it. She will stay with her eggs until her spiderlings are prepared to go. Once her spiderlings are off, she can then resume doing her own business.

Other Information and Tips

These spiders are not considered dangerous to humans. They are even considered beneficial since they control insect population that includes mosquitoes and other pests. Although they may bite to defend themselves, but this still does not pose a threat.

Photo: Six-spotted fishing spider by Benny Mazur, used under CC BY 2.0 / resized from original