Peg Moses, age 12, of Chester, Pa., for her question:

DOES THE HERMIT CRAB BORROW SHELLS?

Hermit crab is the common name for any number of marine crabs and for a number of terrestrial crabs. They are found on or just off the coast of Europe and the Americas.

Hermit crabs, also called robber crabs, are armoriess animals. They insert their abdomens into gastropod mollusk shells that they carry around the with them for protection. The abdomens of the crabs are soft and asymmetrical, flexed and twisted to fit into the whorls of the borrowed shells.

The abdominal appendages of the hermit crab are especially modified for keeping the shell firmly supported on the body.

Hermit crabs are often forced to seek new shells because they have outgrown their old ones. They change their housing whenever chancing upon another shell into which they can fit.

Most hermit crabs are marine. A few terrestrial forms are tropical and belong to the same family as the coconut crab.

The common American species of hermit crab is Pogurus longicarpus.