Wondrous Wildlife – October 2010

Wondrous Wildlife

By Vern and Lori Gieger

Not so Merry Black widow


Mexico is home to an array of insects and spiders, one of the most dreaded is the notorious black widow. Although they are small these little dynamos pack a punch, and are common here Lakeside.

Black widows vary in appearance; the mature female is shiny and black in color, with a red marking in the shape of an hourglass on the underside of her very rounded abdomen. There are variations in the size of females, particularly in egg-carrying females. The abdomen of a gravid female can be more than 0.5 in diameter. Many female widows also have an orange or red patch on the top of the abdomen. The male is either black, or similar to the appearance of juveniles in color, typically a very shiny dark brown, and much smaller with a body of less than 1/4 inch. Juveniles have a distinctly different appearance to the adults; the abdomen is grayish to black with white stripes running across it and is spotted with yellow and orange.

The female deposits her eggs in a silken container in which they remain camouflaged and guarded. A female black widow spider can produce four to nine egg sacs in one summer, each containing 100-400 eggs. The eggs incubate twenty to thirty days; approx. one hundred survive. On average, thirty will survive through the first molting, because of cannibalism, lack of food, or proper shelter. In about two to four months black widow spiders mature enough to breed; however full maturation typically takes six to nine months. Females can live up to five years, while a male’s lifespan is much shorter. The female, on occasion, eats the male after mating; hence the name black widow. Life spans depend upon environment, with shelter being the greatest determining factor and food the second greatest. Males that escape being consumed by the females can go on to mate with other females. It is a widely held misconception that females always eat males after every mating.

Although these spiders are not large, their venom is extremely potent. Compared to other species of spiders, their chelicerae are not large or powerful. In the case of a mature female, the hollow, needle shaped part of each chelicera, the part that penetrates the skin, is just long enough to inject the venom to a point where it can be harmful. The males, being much smaller, inject far less venom. The actual amount injected, even by a mature female, is very small in physical volume. When the venom is diffused throughout the body of a healthy, mature human, it usually is not sufficient to be fatal, though it does produce very unpleasant symptoms; deaths in healthy adults from bites are relatively rare. However, if one is bitten, it is necessary to seek medical treatment immediately.

Black widows tend to seek shelter in dark, undisturbed places such as a wood pile, storage areas, etc. One unique characteristic of their web is the extreme elasticity. It is so resilient it was at one time used by scope manufactures for the crosshairs.

Note: For clarification; we do not receive any financial support from Lakeside Friends of the Animals, or any other organization. We rely 100% upon private donations for animal rescues, their medical treatment and care until they are ready to be released.

For more information about Lake Chapala visit: www.chapala.com

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