How do I kill the crabs???

[dichuy]

I'm moved along in the game pretty well so far (I even made myself a map of Port Royal and list all the people and what they offer me). But for the life of me I cannot seem to figure out how to kill the craps. Am I just lame here? ALso, would love to know if I get rid of the pesty wasps with my sword? I'm killin me lots of guards and skeletons at least!

Thanks for any help you can give me.