Crab Spiders

Scientifically known as Thomisidae, this is a spider family with many species resembling crabs. Although the term is applied to species of other families as well. But, most crab spiders belong to this Thomisidae family. The spiders carry their front two legs in a way that they look similar to crabs, and hence the name is given. This particular family has around 1,200 species in 175 genera. They are ambush predators and move sideways with their long legs.

Crab Spiders

Spiders Belonging to this Family


Physical Description and Identification


Size: The average range of their size is 0.11-1.2 in (0.27-3.0 cm). Most species are around 0.43 in (1.1 cm). Females are always bigger than males.

Color: It ranges from orange to white, brown to red. The flower crab spiders are known for their beautiful patterns. Also, spiders of the Camaricus genus showcase colorful bodies.

Other Characteristic Features: Sexual dimorphism is observed, and they are either through colors or size.


Female crab spiders make two flat egg sacs, joined together, to lay their eggs in. The egg sac is purposely attached to vegetation for protection. The female spider rigorously guards eggs until they are hatched.


It takes around 3 weeks to hatch and by this time the mother dies of starvation. Spiderlings showcase the same coloration as adults’. They go through several molting phases.

The Web

Crab spiders do not build webs for catching preys. They quietly sit down amidst flower and track their preys, before pouncing on them. After catching, they inject their victim with venom to paralyze the body.

Are Crab Spiders Venomous

Crab spiders of this family do not bite humans unless it is absolutely necessary for self-defense. Their bite is not fatal for humans.

Quick Facts

DistributionThroughout the world
HabitatFlowers, grass, leaves
DietFlies, butterflies, honeybees, and other insects
LifespanAround 1 year; in tropical areas the lifespan may be longer

Did You Know

  • Goldenrod crab spider, belonging to this family, can change its color to camouflage with the flower they stay.
  • The name of the family has derived from a Greek word “Thomis” that means long.