Arthur John Thomson,The outline of natural history , Londres, Newsnes, 1945, p. 625.

…when we see the hermit crab’s tail for it soft and flaby without the usual number of limbs and verry much in need of protection. And just as the caddis-fly larvae in the stream encase themselves in cleverly built tubes of cemented pebbles or tiny pieces of stick, and just as some crabs mask themselves with sea-weeds and sponge and such-like things, so the hermit crab makes up for what is much more than « a joint in its armour » by borrowing the substantial shell of some sea- nails which serves at once for protection and for disguise.