Up until the end of the 19th century lobster was so plentiful that it was used for fish bait. Alas, with lobster's ever-increasing popularity (and price), those days are gone forever. This king of the crustacean family has a jointed body and limbs covered with a hard shell. The most popular variety in the United States is the Maine lobster, also called American lobster. It has 5 pairs of legs, the first of which is in the form of large, heavy claws (which contain a good amount of meat). Maine lobsters are found off the Atlantic coast of the northern United States and Canada. They have a closely related European cousin that lives in Mediterranean and South African waters and along Europe's Atlantic coast. Spiny lobsters (commonly called rock lobsters) are found in waters off Florida, Southern California, Mexico, Australia, New Zealand and South Africa. They're easily distinguished from the Maine lobster by the fact that all 10 of their legs are about the same size. Almost all of the meat is in the tail because the spiny lobster has no claws. That meat is firmer, stringier and not quite as sweet as that of the Maine lobster. Outside California and Florida, most of the spiny lobster meat sold in this country is in the form of frozen tails, usually labeled "rock lobster tails. " Live lobsters have a mottled shell splotched with various colors, generally greenish blue and reddish brown. Their shell turns vivid red only after the lobster is cooked. Fresh lobsters are available year-round and are most economical during spring and summer. Female lobsters are prized by many for their delectable coral (eggs). Also considered a delicacy is a lobster's tomalley (liver). Because bacteria form quickly in a dead lobster, it's important that it be alive when you buy it. To make sure, pick up the lobster — if the tail curls under the body it's alive. This test is especially important with lobsters that have been stored on ice because they're so sluggish that it's sometimes hard to see movement. Lobsters come in various sizes and are categorized as follows: jumbo, over 2 1/2 pounds; large (or select), from 1 1/2 to 2 1/2 pounds; quarters, from 1 1/4 to 1 1/2 pounds; eighths, from 1 1/8 to 1 1/4 pounds; and chicken lobsters, which average about a pound. Lobsters must be purchased the day they're to be cooked. They will die in fresh water, so must either be kept in seawater or wrapped in a wet cloth and stored for no more than a few hours on a bed of ice in the refrigerator. All lobsters must either be cooked live or killed immediately prior to cooking. They may be cleaned before or after cooking, depending on the cooking method and the way in which they are to be used. Though whole lobsters are best simply boiled or broiled, lobster meat may be prepared in a variety of ways. Consult a general cookbook for cleaning and cooking instructions. Whole lobsters and chunk lobster meat are also sold precooked. One caveat when buying whole cooked lobster: be sure the tail is curled, a sign that it was alive when cooked. Frozen and canned cooked lobster meat, as well as raw spiny (or rock) lobster tails, are also available. See also shellfish.