The Black Widow, (Latrodectus mactans), is a poisonous spider of the family Theridiidae, order Araneida. The female, about 1.3 cm (0.5 in) long, is glossy black, densely clothed with microscopic hairs, and marked with a characteristic red hourglass on the underside of the abdomen. The male, which is rarely seen, is smaller than the female and has four pairs of red marks along the sides of the abdomen. The Black Widow is found worldwide in the warmer regions in every state in the United States except Alaska and Hawaii; it lives in a variety of natural and domestic habitats.

The life cycle of the widow spiders are all similar. The female lays approximately 250 eggs in an egg sac which is about 1/2 to 5/8 inch in diameter. The eggs hatch in 20 days and remain in the egg sac from about 4 days to 1 month. The young spiders then molt to the second stage and begin feeding.As the young spiders grow, they construct a loosely woven web and capture progressively larger prey. Male spiders molt 3 to 6 times before maturing. The females molt 6 to 8 times and occasionally eat the males after mating. Generally, the females are not aggressive unless agitated, although they are prone to bite when guarding an egg sac.

The venomous bite of the Black Widow Spider, causes muscle spasms and breathing difficulty in humans and may be fatal. The female is distinguished by a red hourglass marking on its underside.The diet of the Black Widow consists of insects, spiders, and centipedes captured with its web. After mating, the female may ensnare and feed upon her mate - hence the name Black Widow.

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There are several other species in the "widow" family - the brown widow, varied widow, red widow, red-back, northern widow, European black widow and western black widow.

The western black widow, Latrodectus hesperus (photograph), ranges from extreme southwestern Canada, south into Mexico, and east to west Texas. Hesperus is the common black widow of the western United States, and is abundant in regions of Arizona, California, and other westerly locales. One of its favored natural habitats is in abandoned rodent holes, but it is often found around human habitations, even in the "downtown" districts of many western U.S. cities. The western widows' general appearance is very similar to that of the southern widow; the "hourglass" marking in the western widow is usually shaped like a perfect hourglass, though it is devided into two seperate "spots" in some specimens. Like its southern cousin, the western widow causes a large number of bites, particularly in the southern part of its range.

The northern widow, Latrodectus variolus, is the third black widow found in the United States. It is found from extreme southeastern Canada, throughout the New England states, and south to northern Florida. It prefers undisturbed wooded areas, stone walls, stumps, and similar habitats. The "hourglass" of the northern widow is usually devided into two separate, elongate markings. This species is most common in the northern part of its range. While its venom is very similar to that of the southern and western widows, and bites do occur, it does not appear to bite humans as often as those species.

The red widow, Latrodectus bishopi, is a U.S. species with a restricted range, being found only in palmetto fronds of sandy, scrub-pine regions of central and southern Florida. This spider is rather brightly colored, with red legs and cephalothorax (fore-part of the body), and a black abdomen with orange and white markings down the back and sides. The "hourglass" usually consists a single red elongate marking. Little is known of the bite of the red widow, but its venom is probably quite toxic to mammals.

The brown widow, Latrodectus geometricus, is a cosmotropical species, found in most tropical seaports around the world; it is an introduced species in Florida. Coloration may vary, but is usually brown to grey, with white and black markings on the back and sides of the dorsal abdomen: The "hourglass" is usually complete. This species is often found on or around human habitations and other buildings. While definitely venomous to humans, bites tend to be less severe than those of most other widow spiders.

The malmignatte, or European black widow, Latrodectus mactans tredecimguttatus, is the common widow spider of southern Europe (northern Mediterranean). It is black, with a series of red markings on the dorsal abdomen. The malmignatte is a significant medical problem in various parts of its range. In Herzegovina (the former Yugoslavia) this spider reportedly causes a large number of bites each autumn in field workers harvesting grain by hand.

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