Cheiracanthium, commonly called yellow sac spiders, is a genus of araneomorph spiders in the family Cheiracanthiidae, and was first described by Carl Ludwig Koch in 1839. They are usually pale in colour, and have an abdomen that can range from yellow to beige. Both sexes range in size from . They are unique among common house spiders because their tarsi do not point either outward, like members of Tegenaria, or inward, like members of Araneus), making them easier to identify. The name is a reference to the backwardly directed process on the cymbium of the male palp. The species epithet is derived from the Greek , meaning "hand", and Acanthium, a genus of thorny-stemmed plants. Venom Though they are beneficial predators in agricultural fields, they are also known to be mildly venomous to humans. Painful bites may be incurred from species such as C. punctorium in Europe, C. mildei in Europe and North America, C. inclusum in the Americas, C. lawrencei in South Africa and C. japonicum in Japan. Cheiracanthium venom is purportedly necrotic, and can cause pain, swelling, and lesions in humans, but the necrotic nature and severity of its bite has been disputed. A study of twenty confirmed Cheiracanthium bites in the United States and Australia found that none resulted in necrosis. Misconceptions A theory that these spiders were attracted to the smell of gasoline was involved in a series of consumer vehicle callbacks in which spiderwebs had blocked fuel lines, but it has since been disproven by a study which found that the juvenile yellow sac spiders were attracted to the hose material itself. Species Cheiracanthium is primarily an Old World genus, with many species found from northern Europe to Japan, from Southern Africa to India and Australia. The only known species in the New World are C. inclusum and C. mildei. While the former also occurs in Africa and Réunion, the latter is found in the Holarctic region and Argentina. They can also be found in the lower mainland of British Columbia, Canada. The genus is quite diverse in Africa and at least three or four species are known to occur in Egyptian cotton fields alone. it contains 214 species, found in the Caribbean, South America, Oceania, Europe, Central America, Africa, Asia, North America, and on Saint Helena: C. abbreviatum Simon, 1878 – France, Denmark C. aculeatum Simon, 1884 – Africa C. aden Lotz, 2007 –