Latrodectus hesperus

Latrodectus hesperus, commonly known as the western black widow spider or western widow, is a venomous spider found across western North America, from southwestern Canada and the Pacific coast through Texas, Oklahoma, Kansas and into Mexico. Females measure 14 to 16 millimeters in body length and are black with an hourglass shaped marking on the underside of the abdomen, usually red but sometimes yellow or white; males are about half the size and generally beige with lighter striping. The species builds irregular, messy webs rather than an organized spiral or tunnel shape. Its venom is a potent neurotoxin that causes pain, nausea, vomiting and localized sweating in humans, though a study of more than 23,000 documented bites between 2000 and 2008 recorded no fatalities.