There is one species of spider.
Latrodectus . The genus contains 31 recognized species distributed worldwide , including the North American black widows ( L. mactans , L. hesperus , and L. variolus ) , the button spiders of Africa , and the Australian redback spider . Spider . They are the largest order of arachnids and rank seventh in total species diversity among all other orders of organisms . , at least 45,700 spider species , and 113 families have been recorded by taxonomists . While the venom of a few species is dangerous to humans , scientists are now researching the use of spider venom in medicine and as non-polluting pesticides .