Anyway, the other day, while giving a program on insects to preschoolers, we found some really cool creatures. One was this incredible, enormous Fishing Spider, most likely Dolomedes tenebrosus. A mom discovered it under a log and I pounced upon it immediately. With a little coaxing, I was able to put it in a viewing jar for all the little munchkins to see. It' s abdomen and thorax alone was about an inch in length. Add the legs and you have about three inches of spider. That is enough to send any arachnophobe into cardiac arrest!
They are fascinating creatures and are called fishing spiders because they many times are found near water. Fishing Spiders can float on the water and catch water insects and even small fish and frogs! They can easily dive under the water, if disturbed. I was surprised we found this one under a log in the woods, but discovered that this particular species is a wanderer. It will often stray far from water and be found in wooded areas, usually on trees or under logs. They are even known to eat gooey slugs. Spiders like these do not spin webs but rely on their speed to overcome and catch their prey.
With only a face a mother could love, this one has eight eyes that are located at the front of the cephalothorax. They are arranged in two rows with four eyes in each row. They have a unique structure found in a few spider groups called a tapetum. This structure is a layer of reflective cells found in the back of the spiders eye. Its function is to increase the amount of light hitting the retina of the spider's eye. This is important for spiders that do not rely on a web to catch their prey, but must rely on sight and speed. If you shine a head lamp in the forest at night, you can observe the eerie glow or eyeshine caused by the tapetum.
This video by National Geographic shows a different species of fishing spider, but you can still get an idea of how they hunt on the water. This one is catching small frogs.