The Thomisidae are 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. (source)