One Extraordinary Spider

Dolomedes tenebrosus derives its name from the Greek for “wily” and the Latin for “dark.”  We call this three-inch spider, one of the largest in Louisiana, the dark fishing spider. The conniving arachnid can be found lurking in the swamps, on the trunks of the bald cypress and tupelo gum near the edge of the water, in search of its supper.  Unlike other, more familiar spiders, the fishing spider doesn’t spin a web on which it waits passively for a meal.  Instead, the wandering spider goes after minnows, tadpoles, and aquatic bugs, sometimes racing across the top of the water to catch its meal.

It hunts from beneath the water’s surface as well.  With a body covered in bristly hairs that trap air bubbles and repel water, the spider can both breathe and stay dry while watching the surface above for passing prey.  Anchoring its back legs onto a tree trunk or the shoreline, the fishing spider is able to remain submerged for up to half an hour. If a spider that can snag a snack while underwater isn’t enough to impress you, then maybe these little-known facts will.

Locomotion by other spiders includes ordinary terrestrial modes of walking, running, and jumping, but a fishing spider exhibits more unusual modes of airborne and aquatic locomotion. They have been reported to glide across the surface of the water in a “freestyle” fashion.  Upon closer observation, scientists discovered that the spider actually sits back on its “hind” legs while simultaneously lifting up its front legs like sails, thereby allowing the wind to propel it forward toward its prey or destination. While not always the most accurate mode of getting around or attacking prey, this is a very energy-efficient mode of travel.  Who knew that fishing spiders were so “green”?

The aquatics performed by a fishing spider consist of more than just a quick dip to catch a minnow.  The spider pushes down on its first three pairs of legs, which propels the spider into the air for a few seconds; after which it lands on the surface of the water.  It performs the motion over and over, appearing to bounce across the surface of the water in a motion similar to a gallop.  The scientists observed the fishing spider galloping as it pursued its prey or fled predators, mainly birds and snakes. 

Fishing spiders are frequently mistaken for wolf spiders due to their similarity in size and color; the distinction between the fisher and the wolf lies in preferred habitats. The wolf spider has eight eyes situated in three rows that allow it to views things from a horizontal plane and is more likely to be found on logs, stone, or the ground.  The fishing spider has eight eyes situated in only two rows, viewing life from a vertical plane, and can be found along the bank or on a tree trunk.  While both species may be found in wooded areas, if you discover one near or on the water in Louisiana, it will most likely be a fishing spider.  

Belonging to a family of spiders casually referred to as “nursery-web” spiders, fishing spiders mate in the spring or early summer, after which the male spider dies suddenly and is then eaten by the female.  After insemination, the female weaves a silky mat, upon which she lays her eggs.  She then wraps silk around the eggs, forming a sphere nearly one inch in diameter.  She carries this egg sac with her chelicerae and pedipalps, which make up her jaws.  The female later attaches the egg sac to foliage high above the ground and spins a “nursery web” around the sac. She stands guard over the nursery web until the spiderlings hatch and watches over them until after their first molt, at which time the baby spiders disperse.  

Because of their large body size, fishing spiders have fangs capable of piercing human skin, and the adult females have been known to viciously strike their prey. Not to worry, though, because they typically shy away from humans, and reports of fishing spider bites are rare; occurring as the result of a spider being smashed inside one’s clothing, for example. 

One rare recorded case of a fishing spider bite reports immediate burning pain at the site of the bite, similar to a wasp or bee sting, followed by redness and minor local tissue necrosis. Although a fishing spider bite contains venom, it only causes illness if the victim is sensitive to spider venoms. 

To be on the safe side, arachnologists suggest appreciating these wondrous arachnids from a safe distance and recommend against handling them. For most of us, that won’t be a problem at all. For those of you who adore spiders and have fond memories of reading Charlotte’s Web, just know that if it walks on water, it’s not Charlotte, and Wilbur won’t be anywhere around! 

(Not really expecting comments on this one, but thought I’d share some of my “paid” work with my readers who might not otherwise see this work.  I hope you enjoyed it, though!)

Preparing for the holidays,

BW