One of 31 known, but possibly 65 in total, Latrodectus species of spiders (family Theriidae) found worldwide except in Antarctica. Typically they are black or dark brown with a red or orange hourglass mark on the underside of the abdomen and varying red or white marks on the upper side. They make irregular, tangled, sticky webs. Their common name refers to the fact that the female may eat the male following mating. Black widows produce a potent neurotoxin, latrotoxin, dilute in males but concentrated in females, and the bite of females is dangerous, although seldom fatal to humans, and the spiders are not aggressive.