Jon Burch Photography
Photograph - Digital Capture/textured
Personally, I don't think anyone should shoot an dead spider more than eight or nine times. That said, let me explain. I'm sure some spiders are harmless and others may even be beneficial. However, I don't like any of them! As a child, I was once bitten in the eye by a spider of some sort. My eye became very swollen as you might guess and I couldn't see for about a week. The upside of this story is that my older sister brought me a baby rabbit to pet and capture my attention. My vision gradually improved, but my distaste for spiders, large or small, black or brown, poisonous or nonpoisonous, did not!
Latrodectus is a genus of spider, in the family Theridiidae, which contains 32 recognized species. The common name widow spiders is sometimes applied to members of the genus due to a behavior seen in some species in which the female eats the male after mating. The black widow spider is perhaps the best-known member of the genus, its bite is dangerous because of the neurotoxin latrotoxin, which causes the condition latrodectism, both named for the genus. The female black widow has unusually large venom glands and its bite is particularly harmful to humans; however, Latrodectus bites rarely kill humans if proper medical treatment is provided.
The prevalence of sexual cannibalism in Latrodectus females has inspired the common name "black widow spider" as the females frequently eat their male partners after mating. The female's venom is at least three times more potent than that of the males, making a male's self-defense bite ineffective. Research at the University of Hamburg in Germany suggests this ultimate sacrifice strategy has evolved to promote the survival odds of the offspring.
Not all adult black widows exhibit the red hourglass on the ventrum underside or top of the abdomen - some may have a pair of red spots or have no marking at all. Female black widows often exhibit various red markings on the dorsal or top side of the abdomen, commonly two red spots. However, black widow young are believed to have at least some sort of marking on their abdomens. Adult male black widows are half the size of the females, and are usually gray or brown rather than black and red; while they may sometimes have an hourglass marking on their ventral abdomen, it is usually yellow or white, not red. Variation in specifics by species and by gender is great; any spider exhibiting a red hourglass or a pair of large red round spots on the ventral abdomen with an otherwise black shiny body is an adult female black widow. The bright red hourglass and spots are never located on the dorsum, which is the more visible aspect; the identifying features are on the underside, anatomically known as ventrum therefore, the spider must be lying on its back to reveal the markings.
Spiders of the genus Steatoda, family Theridiidae family, are often mistaken for widow spiders, and are known as "false widow spiders"; they are significantly less harmful to humans.
In common with other members of the Theridiidae family, the widow spiders construct a web of irregular, tangled, sticky silken fibers. The spider very frequently hangs upside down near the center 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 bite it and wrap it in silk. If the spider perceives a threat, it will quickly let itself down to the ground on a safety line of silk. As 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. While some species are more aggressive, most are not; many injuries to humans are due to defensive bites delivered when a spider gets unintentionally squeezed or pinched. Some bites are thought to result from a spider mistaking a finger thrust into its web for its normal prey, or in cases where a female is protecting an egg sac, but ordinarily intrusion by any large creature will cause these spiders to flee.
Silk from L. hesperus spiders is reputed to be particularly strong compared with the silk of other spiders however, that this is not the case. The ultimate tensile strength and other physical properties of Latrodectus hesperus or western black widow, silk are similar to the properties of silk from other orb-weaving spiders that had been tested. The tensile strength for the three kinds of silk measured was similar however, the ultimate strength reported in a previous study for Nephila edulis was slightly greater. The tensile strength of spider silk is comparable to that of steel wire of the same thickness. However, as the density of steel is about six times that of silk, silk is correspondingly stronger than steel wire of the same weight.
The southern black widow, as well as the closely related western and northern species which were previously considered the same species, has a prominent red hourglass figure on the underside of its abdomen. Many of the other widow spiders have red patterns on a glossy black or dark background, which serve as a warning. Spiders found in multiple regions are listed in their predominant native habitat.
Widow spiders can be found on every continent of the world except Antarctica. In North America, the black widows commonly known as southern (Latrodectus mactans), western (Latrodectus hesperus), and northern (Latrodectus variolus) can be found in the United States, as can the "gray" or "brown widow spiders" (Latrodectus geometricus) and the "red widow spiders" (Latrodectus bishopi). The most prevalent species occurring in Australia is commonly called the redback (Latrodectus hasselti). African species of this genus are sometimes known as button spiders. Lock and load!
Original photograph made with a Canon 5D MkIII camera using a 40 mm macro lens prior to adding the sketching..
April 23rd, 2013
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