The succulent and stupid blue crab is so widely found in the Chesapeake region that anyone who can get to salt or brackish water can almost certainly catch enough to stuff friends and family.

Catching them is such fun that it doesn't need the added incentive of cheapness, and recently some unheraled genius has done a great favor for the weekend crabbers known as "durn chicken-neckers."

The new, cheap and simple "ring trap," apparently anonymously inveted and unpatented, has made it possible for the casual crabber to catch them almost as fast as a waterman, once a good spot is found.

As effective as the complicated and expensive collapsible traps long used be dedicated amateurs, but much easier to use, it costs only $2 to $3. Pull in half a dozen "keepers" and it has paid for itself. Also, because Maryland classifies the ring trap as a dip net, the crabber is not limited. to the maximum of five collapsible traps. You can set out as many as you can handle.

Virginia regulations have not caught up to the ring trap. After hearing one described, a spokesman for the Virginia Marine Resources Commission said, "I think it would have to be classified as a dip net," which requires an $8 license.

"Actually, this kind of trap has been around for a long time," said Charles Schnaitman, who runs a boat-rental and bait shop at Wye Landing, Maryland. "People have been making their own for years. But now the Japanese are making them so cheap it isn't worth the trouble to do it yourself." Schnaitman sells ring traps for $2.25; they're also available at most tackle and bait shops in the Chesapeake region, although many proprietors say they sell so fast they're hard to keep in stock.

The trap -- designed for use off a dock or from a boat, where it can be pulled straight up -- is simply a circle of netting containing two wire rings. Three pieces of string tied to the larger, outer ring support it like a hanging flower basket, and a float where the strings meet helps it sink right side up and keeps the strings out of the way when the trap is on the bottom. A single line tied at the float is used for retrieval. The bait -- a chicken neck, a piece of eel or evan a fish head -- is tied on the center of the netting.

All you do is toss it overboard. When it reaches the bottom the trap lies flat, with nothing to discourage a crab from approaching the bait.

After a few minutes you pull it rapidly to the surface. A crab, when alarmed, heads for the bottom; by the time he's figured out he's in a net, he's in the boat. It's so simple that a novice will become an expert in about 10 minutes. Using six of them from one rowboat, two newcomers last week pulled in more than a hundred Wye River crabs in two hours. One of the virtues of the trap is that it works equally well in clear water, which is the bane of the hand-liner because the crabs often drop off the bait before they come in range of the dip net. Another is that it can also be used effectively in deep water, where the larger crabs are found. And it often brings in several crabs at a time.

It's a good idea to have two bushel baskets handy, one for first dumping the traps and sorting and one for keepers. A heavy glove is advisable for handling them, because even a small crab can nip painfully. After a while you may learn the knack of grabbing them by the base of a backfin, but Schnaitmen, who's been handling them all his life, uses fireplace tongs. What's a keeper? In Maryland the minimum keeper size for a "jimmy" (male) or a mature female crab is five inches from point to point. The male has a long narrow thing on his underside; the female's is large and triangular. An immature female, which has a small triangular plate, may be taken at any size, but the nice thing to do is toss her back so she can make more big, mean males; she's too troublesome to pick anyway.

Soft crabs 3 1/2 inches up are legal (but won't show up in the ring trap, because all they do while their shells are soft after molting is hide). Peeler crabs, just at the point of shedding, may be taken at three inches, but none of us nonwatermen can read a peeler, so toss all the little ones back.

No license is required to take up to a bushel of crabs per person per day for personal consumption. You may use any number of ring traps or collapsible traps, or a trotline no longer than 100 yards. Unlicensed crab pots may be set out only on your own foreshore.

In Virginia the minimum size for males is also five inches. The same size limit applies to immature females, but be a nice person person and toss 'em back to breed. Adult females, peelers and soft crabs may be any size. You may take up to a bushel per person per day for personal consumption.

An $8 license is required for using anything but a handline, including ring traps. To find the nearest licensing agent, call the Virginia Marine Resources Commission in Newport News: 804/245-2811. With the license will come a folder giving details of the regulations, which are complicated. WHERE TO CATCH 'EM -- Callinectes sapidus, the "beautiful and tasty swimmer," is found in salt and brackish water throughout the Chesapeake region. Some can be caught almost anywhere, but larger concentrations are often found around docks and harbors where fish are cleaned, for the blue crab is a bottom-feeding scavenger.

Another strong indicator is the floats that mark where commercial crabbers have put out their pots. If you see lots of floats there are likely to be lots of crabs in the area. But it is considered bad form to crab right in amongst his sets, and may even be unhealthy. Stay off a respectable distance.

If you have a marine chart of the waters you're fishing, look for a dropoff or the edge of a channel in 20 to 30 feet of water. If a spot has not produced some keepers within half an hour, try another one. Crabs are means rascals, but seem to congregate, possibly to fight, so if you're going to catch any you should catch quite a few. Watermen say the biggest crabs are most active at dawn.

The best knowledge is local knowledge, and (private) crabbers are less protective of their "sweet spots" than other fishermen. Ask around at docks and boat ramps. And, mainly, look for people crabbing.

Even rival watermen acknowledge that the Wye River crabs are probably the fattest and tastiest in this region -- which is to say the best in the world -- and there is the further advantage that the Wye is just across the Bay Bridge, an hour from downtown Washington. Grabs can be handlined from the shore, but better catches generally come from a dock or boat.

Schnaitman's Wye Landing is the only place on the river where boats and equipment may be rented, according to the Maryland Wildlife Administration, but he has scores of rowboats ($11 a day) and supplies bait, traps and advice. Fair-sized crabs can often be caught from his dock or the adjoining public boating landing. To get there, take Route 662 off U.S. 50 just past Queenstown and follow the sighns to Wye Oak State Park. After pausing to take in that magnificent tree and lovely Wye Church, turn right on Wye Landing Lane, the next paved road. The telephone number is 301/827-9811. BUYING LIVE CRABS -- If you don't have the time or inclination to catch your own, fine crabs are usually available from the fishboats along the Maine Avenue Wharf. Most of the sellers are nice people who are jealous of their reputations and will not steer you wrong, but it helps if you seem to know what you're talking about.

In the first place, you want males; if you ask for "jimmies," the man probably will pay closer attention. Furthermore, unless price is critical, you want "No. 1 jimmies," which cost about $10 a bushel more but are easier to pick and yield enough more meat to justify the price -- a six-inch crab is more than 20 percent larger than a five-incher, and the ratio keeps going up. But : there is no legal standard for No. 1s, so all you are assured is that they will be the biggest and heaviest ("fattest," in waterman's parlance) males available that day. Prices will vary from about $45 to $30, depending upon the very volatile market; one of the strange things about crabs is that the price tends to fall as the season progresses, although the crabs run steadily bigger and meatier until the first northeaster of the fall puts an end to the harvest.

Unless there is a crab glut on, No. 1s probably will be sold only by the bushel, which should contain no more than about seven dozen and perhaps as few as five dozen, if they're really running big. If that's too many, go shares with a neighbor or invite more friends over, because picking small crabs is so tedious and unrewarding you'll have to snack on something between them to keep up your strength.

When you buy a bushel the man should shift them from the shipping basket into another one, one by one, to pick out the dead ones. If he balks, go to another boat. And the basket should be crammed full.

Better crabs may often be obtained at lower prices from the dockside wholesale houses, where the crabbers sell their catch, but the difference is not likely to be worth the trip unless you're already in the bay area or are buying several bushels for a feast.

Because everybody else wants crabs on the weekend, too, it is wise to put in your order ahead of time; by Friday there often is not a No. 1 jimmy to be had for love nor money. AND FIXING THEM -- Just because nearly everybody cooks crabs by loading them up with salt and spice in a steamer doesn't make it right. You wind up with swollen lips and a stunned palate that can't appreciate the delicate flavor of the meat; it's like making love with gloves on.

Hot spice is terrific with crabs, but use finesse. In the bottom of the steamer put: 2 quarts of plain white (cheap) vinegar 1 cup of spice/salt mixture 1 bottle (2 oz.) of Tabasco sauce.

The steam this mixture produces will penetrate the crabs better than a whole heap of spice dumped on top of them, and won't get the stuff all over your face. If you want them spicier still, shake a bottle of Tabasco over the crabs in the cooker when they've just started to turn red; a few minutes before removing them, pour a beer or a couple of cups of vinegar over them slowly, to rinse the surface Tabasco off.

The faster the crabs cook the better, and the best way, because it doesn't stink up the house, is to do it outdoors on a big round grill. Line it with heavy aluminum foil, letting the edges extend above the edge to reflect heat toward the pot, and then pile in as much charcoal as it will hold.

How long to cook them depends upon how furiously the pot boils and how cold the crabs are to begin with. Whenever they turn bright red they should be done; test it by pulling a claw off one and trying it.

If you've never cracked a crab there's no way to describe how to do it. Get somewone to show you. Your mentor no doubt will tell you to avoid the yellow stuff in there, which is fat and is delicious, but a true crab connoisseur will be seen slipping around the table slurping it up from other's castoffs. Some of us eat the guts too, but that's pretty advanced.