I'm sitting here with shmutz on the front of my instep on one foot, and the back of the heel on the other. I nver had this problem before....

Does anyone know if I should pretreat them, or...

are you wearing new shoes? Sometimes certain shoes make the feet of tights black....

Try to use some water on it while you're wearing them.

Eew. Then your feet get all wet and slippery, as does the shoes.

for about 5 minutes, and then they dry. Wait...I just realized that I was talking about mud splatters.

I would just soak it for a few minutes with "Forever New" which is the gentle washing powder that you can get in lingerie depts. That will take out everything is just a couple of minutes.