Dolomedes

The genus *Dolomedes* includes a group of large spiders known by many names. People often call them fishing spiders, raft spiders, dock spiders, or wharf spiders.

Most species in this genus are semiaquatic, meaning they live partly on land and partly in water. One exception is *Dolomedes albineus*, which lives in trees in the southeastern United States. The name *Dolomedes* comes from a Greek word meaning wily or deceitful. This name reflects their clever ways of surviving near water. They are important members of their ecosystems because they act as predators for many different creatures.

These spiders use specialized tools to hunt on the water's surface. Instead of building a traditional web, they use the water itself as a hunting ground.

They often hold onto the shore with their back legs while their body rests on the water. They stretch out their front legs to feel for vibrations. These spiders have very sensitive hairs called trichobothria on their legs and feet. These hairs allow them to detect movement in the water. They can tell the difference between a struggling insect and a falling leaf. They can even determine the distance and direction of the prey.

Once they identify prey, the fishing spider moves quickly to catch it. They run at pace across the surface tension of the water.

They use their foremost legs, which have small claws, to grab the prey. After catching it, they use hollow chelicerae, or mouthparts, to inject venom. This venom kills the prey and helps to digest it. While they mostly eat insects like mayflies, some larger species can catch small fish. Reports show they have eaten goldfish, sticklebacks, and even smallmouth bass.

Living in water requires unique physical adaptations. *Dolomedes* spiders are covered in short, velvety hairs that are hydrophobic. This means the hairs repel water. This property allows them to use surface tension to stand or run on the water.

They can also dive beneath the surface. When they do, air becomes trapped in their body hairs. This creates a thin, silvery film of air around their entire body. This film allows them to use their book lungs to breathe while they are submerged. This trapped air also makes them very buoyant. If they let go of a plant or rock, they will float to the surface.

There are over 100 different species of *Dolomedes* found throughout the world. Some examples include *Dolomedes aquaticus* in the forest streams of New Zealand. In Europe, you might find the raft spider, *Dolomedes fimbriatus*, in bogs. Another European species is the great raft spider, *Dolomedes plantarius*, which lives in fens. These spiders can grow quite large. Some females have a leg span reaching up to 10 centimeters. Many species are nocturnal, meaning they hunt at night. This helps them avoid predators like birds, which are active during the day.

It is easy to confuse *Dolomedes* with wolf spiders from the family Lycosidae. However, you can tell them apart by looking at their eyes. *Dolomedes* spiders have eight eyes arranged in two rows. Wolf spiders have eyes arranged in three rows.

You can also look at their body shape. Fishing spiders are often more robust with thickset legs. These strong legs help them tackle prey that might be larger than themselves. Their sense of touch is much more important than their sight for hunting.

Despite their skills, these spiders face many dangers. Birds and snakes are their main predators. Some dragonflies have even been known to catch young spiders. There are also parasites like the Spider Wasp from the Pompilidae family. This wasp stings the spider to paralyze it. The wasp then carries the spider away to lay an egg in its abdomen. When the larvae hatch, they eat the spider from the inside out. Some wasps, such as *Anoplius depressipes*, can even stay underwater to hunt the spiders.

This complex web of predators and prey shows how vital these spiders are to their environment.