LATRODECTUS TREDECIMGUTTATUS PDF

Description[ edit ] Female widow spiders are typically dark brown or a shiny black in colour when they are full grown, usually exhibiting a red or orange hourglass on the ventral surface underside of the abdomen; some may have a pair of red spots or have no marking at all. The male widow spiders often exhibit various red or red and white markings on the dorsal surface upper side of the abdomen, ranging from a single stripe to bars or spots, and juveniles are often similar to the male pattern. Females of a few species are paler brown and some have no bright markings. Male black widow spiders tend to select their mates by determining if the female has eaten already to avoid being eaten themselves. They are able to tell if the female has fed by sensing chemicals in the web. Black widow spiders prefer to nest near the ground in dark and undisturbed areas, usually in small holes produced by animals, or around construction openings or wood piles.

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The male widow spiders often exhibit various red or red and white markings on the dorsal surface upper side of the abdomen, ranging from a single stripe to bars or spots, and juveniles are often similar to the male pattern. Females of a few species are paler brown and some have no bright markings. Male black widow spiders tend to select their mates by determining if the female has eaten already to avoid being eaten themselves.

They are able to tell if the female has fed by sensing chemicals in the web. Black widow spiders prefer to nest near the ground in dark and undisturbed areas, usually in small holes produced by animals, or around construction openings or wood piles. Indoor nests are in dark, undisturbed places such as under desks or furniture or in a basement. Then, before the insect can extricate itself, the spider rushes over to envenomate and wrap it in silk.

As with other web-weavers, these spiders have very poor eyesight and depend on vibrations reaching them through their webs to find trapped prey or warn them of larger threats. When a widow spider is trapped, it is unlikely to bite, preferring to play dead or flick silk at the potential threat; bites occur when they cannot escape.

The blue mud dauber Chalybion californicum is a wasp that, in western North America, is the primary predator of black widow spiders. Spiders of the genus Steatoda also of the Theridiidae are often mistaken for widow spiders, and are known as "false widow spiders"; they are significantly less harmful to humans.

Taxonomy Male L. He concluded the colour variations were variable across the world and were not sufficient to warrant species status, and reclassified the redback and several other species as subspecies of the black widow spider. Pickard-Cambridge and Friedrich Dahl had revised the genus, with each criticising the other.

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