Fishing Spiders are a species of spiders that generally live near water bodies. They sometimes may also go deep into nearby forests to hunt terrestrially. They are quite large and they look threatening. They can stretch their legs more than 70 mm, which is a little bit larger than the palm of the hand of an adult. Like most of the spider species in the world, fishing spiders can bite and poison, but their poison is not dangerous unless you are specifically allergic to it.
Fishing spiders belong to the Nursery-Web family. Female fishing spiders lay their eggs on a silky base plate and then wrap the eggs up into a ball-shaped aggregate. After that, they carry this egg ball in their mouth while looking for a good and safe place to hatch. They build a web and attach their egg ball onto the web, then cover it until the little spiders emerge. There may be hundreds of spiderlings that hatch from one egg ball and at some point, they disperse from the web of their mother using their own silks.
Fishing Spiders’ name comes from their food source and hunting action. They may be able to ambush insects and other little creatures on land, however, they are also able to sink their bodies underwater and hunt small fish and polliwogs. Their bristly hairs grow on their body help to trap air bubbles and they use them to breathe while underwater, waiting enduringly for their preys to come by. They are able to stay underwater for more than 30 minutes while hunting submerged. In the meantime, they can hunt insects skimming or treading above them, on the surface of the water.
Fishing spiders are active mostly during the summer. They can be seen on or near boat docks and marinas. You can also run across them near shorelines They may also be seen near shorelines and riversides. If you want to see them, I advise you to keep an eye on the water surface where they quietly hunt.
The Interesting Nature of Fishing Spiders
Among the creatures that walk on the water surfaces which is a task that seems difficult or even impossible for many, the most talented is the fishing spider (Dolomedes). These spiders exhibit a biological miracle with their walking techniques. For them, the surface of the water is like a dance floor. Fishing spiders lurk at the edges of the pond or water source, and when an insect falls into the water, these spiders run over the water to attack their prey. They can also dip their legs under water and catch floating tadpoles and small fish.
The first task of animals having such a life is to stand on water. Fishing spiders use the surface tension of the water. Water molecules attract each other more than molecules in the air. This molecular attraction makes the surface of the water a rubbery layer. When the spider puts one leg in the water, a dimpled pit forms around it and the water pushes itself back to recover.
Surface tension is not a very strong force; for example, if you leave a stone in the water, it will sink immediately. But fishing spiders are both lightweight and have a waxy sheath that repels water on their feet. In addition, thanks to their long legs, they are able to stand on the water. Long legs mean more surface tension, as surface tension pushes objects above water from their tips. (That is why a needle does not sink when properly placed in water.)
Although the surface tension holds the spider above the water, it cannot make it go anywhere else. The waxed legs of the spider are also not sufficient to step on the water surface. But water creates a surface that is slippery enough for the spider to move.
Fishing spiders use three different species of motion while moving on water. Robert Suter from Vassar College found that these spiders actually row using the pits created by their feet. When the fishing spider moves its foot from front to back, it retracts the pit on the water surface. This pit acts as a shovel as it moves and forms a force that pushes the spider forward with water. In addition, the spider paddles four pairs of legs in the middle. It keeps the front and rear leg pairs motionless. It uses these legs for his movements to keep himself above the water.
There is a limit to the speed of fishing spiders. A spider can either make deep dimples to accelerate or push the pits back faster. Both strategies create greater pressure on the surface of the water, and after a certain point, this pressure reaches beyond the water tension and the pits collapse.
Another type of walk of fishing spiders is galloping. When they need to go faster than 1 meter per second, the spiders take this second gait. They raise their legs to keep them almost vertical, then immerse them in water. A galloping spider pushes its legs down and back, while water reacts against the spider to push it up and forward. The upward movement prevents the spider from sinking, while the forward movement allows the spider to cover a distance. This walk is very similar to the technique used by basilisk lizards when running in water.
However, as this gait is quite difficult for the fishing spiders, they use it when they need speed to catch prey or when they want to escape from danger. When they are in less hurry, they change to a third gait: Sailing. When the wind blows, the fishing spider sometimes lifts the front two legs towards the wind (smaller spiders lift their entire bodies), allowing the wind to push themselves like a sailboat. Since the water underneath the spider has a delicate slipperiness, even the slightest push can carry the spider from its location to the opposite shore. These special designs on the bodies of fishing spiders and the techniques they use in walking are just a few examples of nature’s unique and amazing characteristics.
The Lifetime of the Fishing Spiders
Fishing spiders belong to the Pisauridae Family. They are mostly known by their large and hairy body structures. They have black, brown, gray, and white patterns. Although it is hard to distinguish them from wolf spiders, fishing spiders are generally slimmer than wolf spiders. Like all spiders, fishing spiders also have 2 body parts, 8 legs, and fangs (chelicerae) as well as 8 eyes.
Fishing spiders have a simple metamorphosis process. Like all spiders, fishing spiderlings hatch from eggs and resemble small adults when they emerge. While growing, they shed their skin. Female fishing spiders wrap their eggs into a silk ball called an egg sac after laying their eggs. They carry the egg sac in their fangs until it hatches. When it is hatching time, the female fishing spider builds a web where the eggs can hatch safely. This web is called the nursery. It often is formed by one or two leaves which are woven together using silk. This structure functions as a protective pocket where the egg sac can be placed.
Generally, spiders wait motionless for their prey to come close to them as they are ambush predators. However, most of the spiders that belong to the Pisauridae family are actually roaming hunters. They typically search the ground for their preys such as insects, worms, other spiders, and many other small creatures. Fishing (and other nursery-web spiders) can be seen in forests and meadows, especially near water bodies, where they seek for their preys. In particular, they are very common around ponds and streams, and they even hunt on the surface of the still water, generally by holding onto some vegetation at the edge.
Scientific Information About Fishing Spiders
Fishing spiders (Dolomedes) are a genus of large spiders of the family Pisauridae. They are also known as wharf spiders, raft spiders, or dock spiders. Nearly all of the Dolomedes species are semiaquatic, which means they live partly on land and partly in the water. Many Dolomedes species have notable pale markers on each side of their body.
They wait at the edge of a stream or a still water body during hunting, they detect the ripples of their prey, subdue it after running across the surface of the water using their forelegs that have small claws. Then, like nearly all other spiders they inject their venom using their jaws to kill the prey as well as digesting it. Fishing spiders mainly feed on insects, but the larger ones can catch small fish. They can also breathe under the water for nearly 30 minutes using the air bubbles that they collect when they are on the surface.
Fishing spiders have hydrophobic short hairs which means they do not get wet. This feature allows them to utilize the surface tension in order to move and stay on the water surface. Because the air gets trapped in their body hairs it forms a film on the fishing spider’s legs and body, which makes them look like a thin polished silver. This air also helps them to breathe under the water.
Fishing spiders have eight eyes as any other spider, but the more important thing is their sense of touch since they hunt by detecting prey by the vibrations they create on the water surface. These spiders hunt aquatic insects, mayflies, and small fish on the surface of the water bodies such as lakes or rivers, in contrast with most of the spider species which generally prefer to hunt on land or just wait it their webs. We can say that the surface of the water serves as a web for fishing spiders.
Fishing spiders hunt at nights when their main predators, birds sleep. While hunting, they place their back legs on to the land where other parts of their body lying on the surface of the water and their legs are stretched out. Fishing spiders are really strong hunters. They can hunt preys larger than themselves thanks to their thick legs. The stretched out front legs of the fishing spiders help them to sense the vibrations on the water surface. It is the same process as with other spider species since they hunt by waiting in their web, feeling the vibrations. Fishing spiders can also tell what is the cause of the vibrations on the water surface.
In addition to recognizing the source of the vibrations, fishing spiders can also calculate the direction of the prey as well as the distance to it. For this purpose, they develop several vibration-detecting organs which are extremely sensitive hairs on their body. Touching is the essential sense that fishing spiders use to hunt the preys, but it can be said that their eyes also play a role in hunting in the light of recent studies. Yet, this role can be characterized as a secondary role since they generally hunt at night time. They use their vibration detectors to avoid predators such as big fish.
When the spider feels the vibration and senses an insect within its hunting range, it runs across the water surface through its prey and grabs it before it flies and saves itself. Some of the fishing spiders use silk tow ropes not to speed past the insect. Although their essential prey is aquatic insects, since fishing spiders are opportunistic hunters, they eat nearly anything that they can kill. Some fishing spiders have been observed hunting small goldfish.
Their predators are mostly snakes and birds. Dragonflies may also hunt young spiders. Some parasitic wasp species may feed on the fishing spiders by stinging the spider to paralyze it, and then carry it off before laying an egg in it. Then, the egg of the wasp hatch and larvae start to eat the spider inside. Fishing spiders sometimes disappear under the water surface to escape from the wasp attack. But wasps may go deep into the water surface and sting the spider before carrying it out paralyzed.