A black spider with a red back and thick fuzzy legs is commonly called a jumping spider. The formal name is Phiddipus audax.
How many legs (on) a red back spider? if this is the question... 8 (eight) legs less if they have been crushed or ripped off
A black spider that has a red stripe on the back is possibly a red spotted ant mimic spider. They walk on six legs instead of eight and can be found in Arizona.
you have found aRED BACK SPIDER! watch out. poisonous
Often called a zipper spider or writing spider.
It can just be a red back spider...
It can be hard to tell what kind of a spider you are looking at that has a red head and back and black and white striped legs, since the body type is also an important factor. Chances are that it is a red-headed jumping spider, which can cause a somewhat painful bite but is not otherwise dangerous to humans.
an indonesian ondrius (very rare)
The Red-back spider (Latrodectus hasselti) is commonly found in Australia. They are a small black venomous spider with long thin legs, and the females have a red stripe on their globular abdomen.
red widow
It isn't a spider at all. It is an insect masquerading as a spider. I live in Tennessee and on June 19 encountered one on my porch. I killed it and the "body" fell off. On further inspection I found it only had 6 legs.
a wolf spider. they hurt but are not deadly to humans