The black orange spot house spider is also, and more commonly, known as the redback spider. These are native to Australia and belong to the widow spider family. They are found throughout Australia and have also been located in New Zealand and Japan.
The female spiders are usually black and have a red or orange spot or stripe on top of the abdomen. The abdomen is very rounded. Like their black widow cousin, these spiders also bear the characteristic hourglass marking underneath the abdomen, which is usually orange or red in color. Young redback spiders have whitish-colored spots on their abdomens.
The males have more elongated abdomens and are smaller than the females, which are approximately a centimeter in body length, or about .4 inches.
The redback spider's web looks like an irregular mess of fibers with no distinctive pattern to be discerned. The silk is very fine, but quite strong. The web contains a funnel area for the spider to retreat and also keep its egg sacs.
Redback spiders will create their webs in sheds, logs, woodpiles, on porches or outdoor furniture, potted plants, or in piles of debris. Prey generally includes insects and other spiders, but a redback spider will sometimes prey upon larger animals such as lizards. They like warm, dry locations. The redback seems to prefer having its web in a sunny area, but with a nearby crevice of some sort where it can insert part of the web.
When attempting to mate, the males will perform a sort of courtship, which includes tapping on the female's web and wrapping it in his own silk. Interestingly, once mating takes place, a female can store the male's sperm for up to two years. The female will create egg sacs in which she can deposit up to 300 eggs. The spiderlings usually hatch in about two weeks and will disperse by ballooning, or riding air currents.
Like the black widow, the bite of the female redback spider is of concern and can be dangerous to humans. If bitten, a person may experience pain, swelling, and redness at the site of the bite. Other symptoms may include fever, convulsions, nausea or vomiting, or weakness. A victim can apply ice, though not pressure, to the bite location, and seek medical attention. As always, it is helpful to bring the spider along for identification, if possible. There is anti-venom available for redback spider bites.