Redback spiders are members of the widely distributed Latrodectus genus known as widow spiders. Other members include the black widow (L. mactans) and brown widow (L. indistinctus) of North America, the thirteen-spotted spider (L. tredecimguttatus) of Europe and the katipo (L. katipo) of New Zealand. In Australia, redbacks vary considerably in numbers from region to region and suburb to suburb. Although widely distributed, they are more common in temperate regions than the colder, southern areas. Redbacks have adapted well to an urban environment, making their homes in sheds and garages, under houses, in industrial areas and in outside toilets. Redback spider bite is thought to be the commonest serious spider bite in Australia, particularly over the summer months. An antivenom was introduced in 1955 and no deaths attributed to treated redback spider bites have been reported since. Prior to this, at least 14 fatalities had occurred.