These venomous, shiny black spiders are the best known and largest of the comb-footed spiders. Black widows are solitary and spend the majority of their lives patiently waiting for insects to become ensnared in their webs. Females have a distinctive red hourglass marking on the underside of the abdomen while the rarely seen males are smaller, have longer legs and red and yellow markings along their sides. Only the female black widow is poisonous; the males and the young are harmless.

Weavers of Tangled Webs
The webs woven by black widow spiders are about 30cm (12in) in diameter and look messy but they have a definite funnel structure. They usually weave their webs near the ground, in dark places such as the base of small bushes or among heaps of debris. In colder weather, they can often be found in barns and sheds. The female hangs belly upwards and rarely leaves the web. Like many spiders, the black widow has poor eyesight and depends mainly on sensitive body hairs and bristles to detect the vibrations that signal there is prey in its web. This spider will bite in self-defence if touched or if guarding eggs. In spite of its considerable strength, the venom rarely kills humans as only a tiny amount is injected. However, it can cause abdominal pain similar to appendicitis, as well as muscle spasms, particularly in the soles of the feet, and distressing breathing difficulties.

Cannibalistic Young
When the male finds a receptive female he transfers sperm to the female’s body with organs carried in the pedipalps (small feelers on the head). The female then lays several sacs of eggs, containing up to 250 eggs in each, which she protects fiercely. These silken sacs, ranging from white to tan in colour and with a papery texture, are suspended in the web. Normally, only between one and 12 young survive after incubation because the young eat each other. Newly hatched spiders are yellowish-white. They take on more black and varying amounts of red and white markings each time they moult their exoskeleton (outer casing) to expose a new and bigger one underneath to accommodate their growth.

Deadly Injection
Black widows prey on insects, catching cockroaches, crickets, beetles, flies and moths in their sticky webs, which are constructed on three levels. The spider then makes small punctures in its victim’s body and injects venom. This takes one to two hours to work, during which time the spider rests. It then injects digestive juices and sucks out the liquid contents. Black widows also feed on other spiders and centipedes and, in hot dry places, on scorpions. The female avoids light and tends to hunt her prey at night.

This information was brought to you by:
Wildlife Explorer