Subject: Which crustacean builds a protective shell from detritus?

I write for a technology magazine which is running a feature on the use of 
composite materials in vehicle design. We would like to accompany it with a 
picture of an animal that creates its own composite materials - I seem to recall 
a crab or something that builds its own protective casing with small shells, sand 
and stones etc. (I know of the stone fly nymph but can't find good pictures of 
it) Thanks very much! 

Re: Which crustacean builds a protective shell from detritus?