I have a crater in the side of my leg from a Brown Recluse bite about 7 years ago.
Basically, as was described by my doc, the venom acts as the digestive enzyme for the spider. it is potent enough to kill small mammals etc, and on occasion, humans. Anyway, since spiders don't have stomachs, they come back to their kill after the fact and then suck up all of the digested goo from their pray. Aka, my leg ha. Well, if I would have died.
So instead, the venom just liquified muscle, tissue, etc in my leg down to the bone. They had to cut out all of the necrotic flesh/insides in my leg. Permanent nerve damage, etc. It did all of that in about 4 days. My leg swole up like a softball was under my skin.
It looked alot like this, a little bit bigger
So now I have an indentation on the inside of my left leg because of it.
Short story? F spiders.