Help! caterpillars taking over!?

For the last 3 days I get home from work and caterpillars are every where. My whole back door is covered in them, plus the black stuff they spit out! My outside concrete is now covered in stains! What is a natural way to deter them in the other direction away from my house? I hate to kill them but when you have over 50 of them at your back door..it is so annoying! Please help..thank you!