The long-legged sac spiders (familyEutichuridae) include nearly 400 species in about 30 genera worldwide.
The largest genus currently recognized as belonging to this family is Cheiracanthium, which used to be placed in the family of "true" sac spider, Clubionidae. The transfer of the primarily Old World genus Cheiracanthium in the Eutichuridae has been convincingly shown by a spectacular work by Martin Ramírez (2014). Only two species are known from the United States, one of which is obviously introduced. The genus is quite diverse in Africa and at least three or four species are known to occur in Egyptiancotton fields alone. The family would be totally obscure if it were not for the fact that members of Cheiracanthium are documented beneficial predators in agricultural fields and are also known to be mildly venomous to humans. The yellow sac spider, Cheiracanthium inclusum, has been studied more than the other species in regard to its role in controlling pest insects in the southeastern United States. Other genera include the more obscure southwestern US and Mexican Syspira, which superficially resembles a wolf spider (Family Lycosidae).