Crab Spider: How to Identify

The crab spider gets its name because it can hold its legs crabwise and move backward and sideways, not just forward. Mostar crab spiders are a member of the Thomisidae family; however, some belong to the Sicariidae (like the Brown recluse), Sparassidae (like the Huntsman’s spider), or Selenopidae (like Jumping spiders) families.

Researchers now believe crab spiders can change their color over time.

Crab spiders are also called Flower crab spiders, and many, like my favorite, the Goldenrod crab spider, can be found on flowers like roses and goldenrod. In the early Fall, the goldenrod plants around my home are teeming with goldenrod crab spiders, just waiting for the unwary butterfly or grasshopper to land nearby.

I won’t list them as actual predators later, so for now, I will point out that my chickens hunt them down like coyotes after rabbits.

Goldenrod Crab Spider
Goldenrod Crab Spider

Crab spider identification.

Crab spiders come in many colors, including pink, yellow, blue, black, white, and green. The easiest way to identify a crab spoiler is by noting the front four legs that are longer and thicker than the four rear legs. 

The crab spider has eight eyes mounted on a lump on the front of their cephalothorax. They have two forward-mounted claws, flat bodies, and crabwise legs.

The crab spider can change color slightly with each molt, allowing it to camouflage itself against its current background. Some researchers believe crab spiders can even assume the colorations of their prey.

Crab spiders do not make a web, instead using a single start of silk to support themselves. Females wait for prey while sitting patiently on a plant or flower. Male crab spiders hunt while wandering around.

Special crab spider types.

In the Thomisidae family, there are 2100 species and around 175 genera.

The Goldenrod spider is of the genus Misumena, Misumena vatia in particular. They are one of the species of crab spiders known to change color from their normal or resting color to meet their predatory needs.

Bark crab spiders (Bassaniana) live camouflaged amongst the bark of trees while hunting prey.

Oxytate, which turns green to conceal itself in the grass or on a leaf.

Phrynarachne spiders that look like bird poop.

Xysticus cristatus Common crab spider
Xysticus cristatus Common crab spider

What do Crab spiders eat?

The venom of a crab spider is powerfully toxic and allows these spiders to take down much larger prey (seen in the photo above and below). 

Crab spiders eat mostly anything that comes within range. So grasshoppers, butterflies, wasps, bees, aphids, caterpillars, flies, beetles, and other insects are fair game to these potent killers.

And if prey is a scarce, many crab spiders can live off the nectar and pollen from the very flowers they hunt from and mimic.

Goldenrod Crab Spider
Goldenrod Crab Spider

Crab spider: Habitat.

The crab spider is found almost everywhere in the world. Like the U.S. Marines, they are found in every clime and place. They have found homes in the tropics, deserts, forests, and even mountain tops. 

As long as it isn’t too cold or too dry, crab spiders live there, waiting for prey under some tree bark, crawling under leaf litter, or standing motionless and ready on a flower.

Flower crab spider
Flower crab spider

Are crab spider bites dangerous to humans?

Despite the crab spiders’ toxicity, their bite does not create a medically significant wound n those who are not hyper-allergic to it.

Many crab spiders have fangs that are too small to penetrate human skin. But even the Giant huntsman spider rarely produces side effects other than headaches and nausea.

Female crab spiders deposit their eggs in an egg sac woven of silk. They will guard their eggs and hatchlings until their second molt but will die soon after. With the high probability the female ate the father, many crab spiders are born as orphans.

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Dennis V. Gilmore Jr.

Dennis V. Gilmore Jr. is a former Marine Sergeant and the author of several books, including two on night hunting coyotes and red and gray fox. He has written several hundred articles on predator hunting for

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