Leigh Anne Kuper, age 8, of Council Bluffs, Iowa, for her question:

WHAT IS A HERMIT CRAB?

There are about 4,500 different kinds of crabs on earth.    They live in shallow waters along coasts, and also in deep waters. Many of the varieties are used by man as food. Some live in burrows in the banks of salty tidalstreams while others live in fresh water or in burrows that are several miles ashore. A female pea crab lives in the shell of a live oyster.  Most crabs are covered with hard shells and havejointed legs. The color, form and texture of claws, legs and bodies    run through many shades and shapes. Some are smooth while others are either rough or spiny. Some crabs are swimmers and even have paddles on their last pair of legs. Some run sideways on the rocks or sand.

Most common crab sold as food in eastern American markets is the blue crab. When these creatures shed their shells, and the new ones have not yet hardened, they are sold as the extra choice soft shelled crabs.

On the Pacific coast two edible crabs are popular. The Alaska king crab, which is also called the Japanese crab, is a good tasting creature that can weigh up to 12 pounds. In shallow waters from California to Alaska, fishermen catch the popular Dungeness crab.

One of the most interesting of all crabs is one called hermit. He lives alone in the shell of a sea snail. He usually moves in after the snail has died, but sometimes pulls a live snail out to obtain both a feast and a home.

Unlike other crabs, the hermit has soft, unprotected rear parts. He can twist his body into the spiral of an empty seashell. Only his claws stay outside, and he uses them as a tightly fitting door. As the hermit crab grows, he changes his shell for a larger one.

Each hermit crab lives alone in his adopted shell. Large groups often crowd areas of the ocean floor where seashells are abundant. They can be gathered from pools left after high tide, and make very amusing pets.

One kind of hermit crab grows two feet long. He is called the robber crab and also the coconut crab because it is said to climb coconut trees and pick the nuts. This crab lives in burrows which he digs beneath the coconut palms of tropical islands.

The coconut crab, which is one type of hermit crab, does not use an adopted shell the way most of his brothers do. This variety has plates of armor on the rear parts of his body. He has so much stength in his claws that he can easily tear open a coconut for food.

Another most unusual crab is the pine crab. He makes his home in bromeliad plants that grow on tropical trees. He lives in water that collects at the bottom of the plant.