Richard York, age 16, of Thornton, Ky. for his question:

What are crustaceans?

The crustaceans are the crusty ones of the animal kingdom. The lobster is a crustacean and so is the crab. The lobster lurks in an underwater ambush, waiting to pounce upon a passing fish. The crab keeps his sharp pincers always ready to take a nip at your toe. These fellows are certainly crusty, crabby characters. And both wear crusty coats. The class name Crustacea refers to the crusty coats and not the crusty characters of these creatures.

Crustacea is a class of animals, a sub division of the huge phylum Arthropoda, meaning those with jointed feet. The members of Arthropoda outnumber all the other animals in the world by six to one. The crap and all his crustacean cousins are also arthropods.

To qualify as an arthropod, an animal must have special joints. Since he has no bones, this is not easy, His soft inside body is supported by armor or a tough skin. The joints are leathery rings where the rigid skin is bendable, Muscles attached to the inside straddle across these joints. The arthropod can bend his legs by stretching and shrinking these muscles. An arthropod will have several pairs of jointed legs, ending in jointed feet. He may also have a pair of jointed antennae and a jointed tail,

The soft body inside is filled with fluids which are kept circulating by a heart which is a simple tube, open at one end. Every arthropod needs oxygen, though some get it from the water and some from the air, The arthropods noses through which he takes in air or water, is a series of holes in the armor along his sides.

By now you have guessed that insects are arthropods.

Spiders and scorpions also belong in the Arthropoda phylum. And so do the crusty crustaceans. Most members of the Crustacea class are water breathing arthropods.  Though he qualifies as an arthropod, the crustacean has special features which make him different from the insects and the spiders.

His outer coat is usually made of tough armor called chitin.  The head and thorax are encased in a one piece shell. The crustacean has no waist and no neck. Most crustaceans have five pairs of legs and two pairs of antennae, all jointed.

The class Crustacea includes the lobsters, the shrimps and the barnacles and a vast assortment of water fleas and sand fleas. The common crabs are crustaceans, but not the king crabs The giant of the class is the Japanese crab who may measure ten feet over the top of his. shell, The midgets are water fleas who may measure 100 to an inch,