The female spins up to 8 round balls of web for her eggs. Some of these may contain as many as 300 eggs. If the weather is warm, the spiderlings hatch after about 2 weeks and will moult several times as they grow before they reach full size. If disturbed while guarding her eggs or cornered, she will bite the intruder with her small but effective fangs. Most bites occur when the spider is trapped against the skin e.g. when clothes are put on that contain a spider, or picked up in rubbish.
Most bites occur on the hands or feet than the rest of the body.
Although this spider injects only a tiny amount of venom, it can cause serious illness and deaths used to occur before an antivenom became available in 1956. The action of the venom is unique as it can attack all the nerves of the body and in serious cases cause a paralysis which may lead to death. At first the bite is only as painful as a minor insect sting, but after a few minutes it becomes intense and spreads to other parts of the body. A special feature seen only with Red-back bites is that the bitten limb may sweat profusely while the rest of the skin remains dry. Fortunately the serious affects of the venom take several hours or even days to develop and there is plenty of time for treatment with antivenom.