What is a Black Widow Spider


The name black widow spider (latrodectus mactans) includes several varieties of related arachnids found in warm and temperate regions around the world. Like other spiders, they have two body sections: the cephalothorax which bears the head and legs and abdomen where the spinnerets are located.

Black widow spiders have 4 pairs of legs and 8 simple eyes. They are nocturnal, generally shy and reclusive and cannibalistic. A female will sometimes devour the male after mating occurs, hence the appellation “widow”.


Female black widows have a shiny, black or dark brown, two-part body which measures about 1 1/2 inches across. There is a distinctive red hourglass shape on the underside of the abdomen. Males are smaller, about inch across with longer legs and red and yellow markings. Both sexes have strong jaws, poisonous fangs and a hard exoskeleton.


From the spinnerets the female produces strong strands of silk to make a tangled-looking web usually in dark, sheltered places near the ground. Webs may be one foot in diameter. They are often found in woodpiles, under stones, in hollow stumps or rodent burrows. Indoors, they may be in sheds, garages, outhouses. These spiders prefer cluttered areas where they won’t be disturbed.

The web is used to trap food and the female will not leave her web voluntarily. At night, she will hang belly-up from the centre. The tips of her legs are oily, so she won’t get trapped in the web herself.


Black widows eat flies, moths, crickets, small reptiles and other small animals. Their fangs inject venom and digestive liquids into the prey. This kills it and makes it easy for the spider to eat.


Mating takes place in Spring or Summer. The female lays from 25 to 250 eggs in a white, silken sac suspended from the web. The sac is pear-shaped and turns tan or grey in a few days. It is about 1/3 to inch in diameter. Several egg sacs may be produced during one summer.

The incubation period lasts about 4 weeks. The spiderlings hatch and molt once while still inside the sac. When they emerge, they disperse by ballooning, extruding silk threads and being carried away by air currents. They molt several times before reaching maturity in 2 to 4 months. They are often eaten by their siblings or by predators before they mature.

Female black widows live about a year, males about four months.


These spiders consume a large number of insect pests: flies and mosquitoes which carry disease, locusts and grasshoppers which destroy crops and beetles and caterpillars which damage trees. Thus, they help maintain the balance of nature.

Their venom may help in the discovery of environmentally-safe insecticides. It could also aid in the development of drugs to help heart attack patients because it has an immediate effect on blood vessels.


The female adult black widow is the most venomous spider in North America. Its venom is 15 times deadlier than that of the prairie rattle snake, yet it is seldom fatal to humans. Only children, the elderly, and those with health problems are in danger of death from its bite.

The male and the spiderlings pose little danger to anyone and the female will usually only attack in self-defence or when she’s guarding her egg sac and feels it is threatened.

If a human is bitten by a black widow spider, medical aid should be sought, just to be on the safe side. The bite can be very painful.

Needless to say, a black widow spider should not be picked up and examined when discovered in the wild, nor does it make a suitable object of study in a terrarium in the classroom.