more at http://quickfound.net/
Scientific Consultant: Evert I. Schlinger, Ph.D. (University of California).
Script Editor: Robert L. Patton (Riverside City Schools).
Photographer and Director: Ken Middleham.
Originally a public domain film from the Library of Congress Prelinger Archives, slightly cropped to remove uneven edges, with the aspect ratio corrected, and one-pass brightness-contrast-color correction & mild video noise reduction applied.
The soundtrack was also processed with volume normalization, noise reduction, clipping reduction, and/or equalization (the resulting sound, though not perfect, is far less noisy than the original).
Latrodectus is a broadly distributed genus of spiders, which is composed of both black widow spiders and brown widow spiders. A member of the Theridiidae family, this genus contains 31 species, including the North American black widows (L. mactans, L. hesperus, and L. variolus), the European black widow (L. tredecimguttatus), the Australian redback black widow (L. hasseltii) and the button spiders of Southern Africa. Species vary widely in size. In most cases, the females are dark-coloured and readily identifiable by reddish markings on the abdomen, which are often hourglass-shaped.
These small spiders have an unusually potent venom containing the neurotoxin latrotoxin, which causes the condition latrodectism, both named after the genus. Female widow spiders have unusually large venom glands and their bite can be particularly harmful to large vertebrates, including humans. Only the bites of the females are dangerous to humans. Despite their notoriety, Latrodectus bites rarely cause death or produce serious complications…
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.
Like other members of the Theridiidae, widow spiders construct a web of irregular, tangled, sticky silken fibres. 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. The spider frequently hangs upside down near the centre of its web and waits for insects to blunder in and get stuck. Then, before the insect can extricate itself, the spider rushes over to envenomate and wrap it in silk. To feed, the mouth pulses digestive juices over the prey which is liquified and then internalized by capillary action, allowing the slurry to be sucked back up into the mouth. Their prey consists of small insects such as flies, mosquitoes, grasshoppers, beetles, and caterpillars. If the spider perceives a threat, it quickly lets itself down to the ground on a safety line of 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. Many injuries to humans are due to defensive bites delivered when a spider gets unintentionally squeezed or pinched. The blue mud dauber (Chalybion californicum) is a wasp that, in western North America, is the primary predator of black widow spiders…