Well, there is a generic term 'scavenger crab' that covers any crab that scavenges for food.

More interesting, a street cleaner is also referred to as a 'scavenger crab'; hadn't heard that before.

If you're interested in taking a look at many different types of crabs, check out the crab list on OneLook:

http://onelook.com/?w=*crab&ls=a