Thomisidae

Thomisidae is a family of spiders, including about 175 genera and over 2,100 species. The common name crab spider is often applied to species in this family, but is also applied loosely to many other species of spiders. Among the Thomisidae, "crab spider" refers most often to the familiar species of "flower crab spiders", though not all members of the family are limited to ambush hunting in flowers.

"Crab spider" as a name in common use

Rationalisation for the name crab spider is generally subjective and anecdotal. It is commonly said to refer to a fancied resemblance to crabs, or to the way such spiders hold their two front pairs of legs, or their ability to scuttle sideways or backwards. Some spiders so called have bodies that are flattened and angular. At all events, the Thomisidae are the family most generally referred to as "crab spiders". However, some members of the Sparassidae are called "giant crab spiders", Selenopidae are called "wall crab spiders", and various members of Sicariidae are sometimes called "six-eyed crab spiders". Some unrelated orb-weaver spider species such as Gasteracantha cancriformis also are commonly called "crab spiders".