Latrodectus hesperus

Latrodectus hesperus, the western black widow spider or western widow, is a venomous spider species found in western regions of North America. The female's body is 14–16 mm (1/2 in) in length and is black, often with an hourglass-shaped red mark on the lower abdomen. This 'hourglass' mark can be yellow, and on rare occasions, white. The male of the species is around half this length and generally a tan color with lighter striping on the abdomen. The population was previously described as a subspecies of Latrodectus mactans and it is closely related to the northern species Latrodectus variolus. The species, as with others of the genus, build irregular or 'messy' webs: Unlike the spiral webs or the tunnel-shaped webs of other spiders, the strands of a Latrodectus web have no apparent organization. Female black widows have potent venom containing a neurotoxin active against a range of mammals. (See latrodectism.) Symptoms are pain, nausea, goosebumps, and localized sweating. Fatalities have been reported at between 0.5% and 12%. The female's consumption of the male after courtship, a cannibalistic and suicidal behavior observed in Latrodectus hasseltii (Australia's redback),is rare in this species. Male western widows may breed several times during their relatively short lifespans. Males are known to show preference for mating with well-fed females over starved ones, taking cues from the females' webs. Latrodectus hesperus can be found in western regions of North America. In Canada it can be found from British Columbia to Manitoba. They are most commonly found near the Canada-US border, as well less commonly throughout prairies regions of the Canadian Prairies in Western Canada. Female stimulates by contact with male webs Male and female Latrodectus hesperus produce sexually specific scents which are combined with their silk; each sex responds by initiating mating when it comes in contact with a web of the opposite sex. Latrodectus hesperus frequently hangs upside down near center of the web and waits for any insects to enter the web to attack. It bites its victim then wraps it in silk. Latrodectus hesperus has a few parasites or predators known to affect them; parasites include wasps in the family Scelionidae and flies in the family Acroceridae, and flies in the genus Pseudogaurax, while the most common predator is the wasp Chalybion californicum. Latrodectus hesperus often live in human dwellings, usually in cluttered dark areas. It has poor eyesight, and detects danger by silk vibration. Only female spiders have fangs long enough to pierce the skin, and so cause a bite to be harmful and require medical treatment.