Yep, hermit crabs use the discarded shells of other critters.. don't make their own... When I moved back from Cuba, I had a shell collection I had gathered on the beach.. the movers just packed everything and it came back on a container ship.. it was well over a month between packing, getting a new place and getting unpacked....imagine my surprise when I unpacked, put my pretty shells in a dish on the endtable and a couple of days later, found the shells under the couch.... yep.. I had a whole colony of the little critters.. none the worse for the trip...