This is a female White Tail which are about 20mm long. the males are about 12mm and quite common in Tasmania. They prefer to feast on other spiders, such as curtain-web spiders, daddy-long-legs, redback spiders and black house spiders.
It is commonly thought that the bite from the white tailed spider causes necrotising arachnidism, an ulcerating sore which is very difficult to heal. The latest research indicates that it is rather the result of other germs which are introduced into the wound which cause the ulceration and not the venom.