The Black Widow (Latrodectus mactans), typically known as the Southern Black Widow, is a species of arachnid that is native to the United States of America. There are two closely related species to the Southern Black Widow; the Western Black Widow (Latrodectus hesperus), and the Northern Black Widow (Latrodectus variolus). These three species are often confused with the genus Steatoda (false black widows). The black widow was first described in 1775 by Johan Christian Fabricius.
The Southern Black Widow is mostly found in the southeastern United States, ranging from Florida to New York, with some as far west as Arizona. The northern black widow is found in the northeastern US and southeastern Canada. Its range overlaps with the southern black widow. In Canada, the black widows are found in British Columbia, Alberta, Manitoba and Ontario. The Black Widow has also been established in the Hawaiian Islands. It is most likely that these inhabitants were transported through imported goods such as produce.
This species is well known for its unique black and red coloring found in the female, and the fact that she will often eat her mate after mating has occurred. The adult female is about 1.5 inches long. She is shiny and black with a red hourglass figure on the underside of the abdomen. Many females have a reddish or orangey patch just above the spinnerets on top of the abdomen. The male is usually all black and less than a quarter of an inch long. The young are grayish or black with white stripes running across the abdomen. There is also yellow and orange spots.
Once a mature male inseminates the female, the female will deposit her eggs in a globe-like silken container in which they remain guarded. The female can produce four to nine egg sacs during the summer. Each egg sac may contain as many as 400 eggs. The eggs incubate for 20 to 30 days, of which only about a hundred survive through this time. On average, about thirty will survive to first molt. Most die because of cannibalism, lack of food, or lack of proper shelter. The survivors are mature enough to breed within two to four months, but usually take several months longer. A female black widow can live for up to 5 years. The male has a much shorter lifespan. Occasionally, the female will consume the male after mating. L. mactans is the only species of black widow that performs this type of sexual cannibalism. If the male escapes being consumed, he may go on to mate with other females again. It is typically thought that the name “widow” is given because the female always consumes her mate when reproduction is completed. This is, however, a general misconception.
The prey of the Black Widow consists of a variety of insects, but occasionally woodlice, diplopods, chilopods, and other arachnids are also taken. Once the prey becomes entangled in the web, the female rushes to the victim, wraps it up in a strong web, then bites the prey, envenoming it. The spider holds tightly onto the prey as the venom takes its effect (usually within 10 minutes). When the prey stops moving, digestive enzymes are released into the wound and the black widow carries the meal back to its retreat for feeding.
The venom of the black widow is extremely potent (reported to be much more potent than the venom of coral snakes and cobras). Compared to other species of spiders, their fanglike pincers (located near the mouth) are not very large or powerful. A mature female has pincers that can only penetrate skin up to about 0.04 inches deep. Still, this is enough to inject the venom to the point where it can be harmful. The male has even smaller pincers and injects far less venom. The volume that a mature female injects, is very little in volume. When the venom is diffused throughout the body of healthy, mature humans, it usually does not amount to a fatal dose. Deaths in healthy people from black widow bites are very rare in terms of the number of bites per thousand people. Only 63 deaths were reported in the US from 1950 to 1959. If taken into consideration, the range of widow spiders is very immense, and as a result more people are exposed worldwide to widow bites than bites from other far more dangerous spiders, so the highest number of deaths throughout the world are caused by members of this genus.