Heres a little info i found.. i posted the link followed by the info given. so you can click the link or read it here. they are also know as sand fleas and are good for bait
the last link even includes prices.
http://images.google.com/imgres?img...=/images?q=mole+crab&svnum=10&um=1&hl=en&sa=N
"Ar-1440 MOLE CRAB, Emerita talpoida, an active small anomuran crustacean living in the surf zone. It burrows vigorously through sand, disappears in seconds, and can be easily studied in the classroom. Size: 1-4 cm."
http://images.google.com/imgres?img...grefurl=http://en.wikipedia.org/wiki/Emerita_(genus)&h=268&w=260&sz=30&hl=en&start=6&um=1&tbnid=Bc8_8biVnXke0M:&tbnh=113&tbnw=110&prev=/images%3Fq%3Dmole%2Bcrab%26svnum%3D10%26um%3D1%26hl%3Den%26sa%3DN
Emerita is a genus of oval-shaped crustaceans found on the Atlantic and Pacific coasts of North and South America. Emerita are popularly known as mole crabs, sand fleas, sand crabs, beach hoppers, or even more colloquially as lookie cookies. Although like true crabs they belong to the order Decapoda, they are classified in a different infraorder, Anomura (the true crabs are in the infraorder Brachyura).
Sand crabs live under sand in shallow water near the shore, and live from two to three years. They have the color of rippled sand at the water's edge and live mostly buried in the sand in the zone where the waves wash up onto the beach, with their antennae reaching into the water forming a V-shaped obstacle in the water as the wave recedes. These antennae filter plankton and organic debris from the water. Mole crabs also eat the tentacles of Portuguese man o' war, which are collected by winding the tentacle around the mole crab's leg. Their camouflage protects them from their predators - chiefly fish and birds.
Females grow to about 35 mm long, and carry their bright orange colored eggs under their telson during the summer months until they are ready to hatch. The eggs remain hidden unless you gently lift up their telson (looks like a tail and is tucked under their bodies). Upon doing so, you can see many small eggs that range from a light orange to a yellow colour. Males are smaller, only reaching 20 mm, making the sexes easy to tell apart when fully grown.
If one is a keen observer, one can spot these small crustacea by the V's they leave in the water as the waves recede, often being found in groups ranging in size from dozens to thousands. They can also be detected by watching for bubbles coming out of small holes in the sand where waves wash up, being buried 2-12 inches below that location. As each wave washes up, they may scurry around to new locations while there is water present, burying themselves just before the water disappears. Some people have fun collecting the crabs by scooping up the creatures from just below the surface of the sand with their hands and releasing them a few feet higher up onto the beach. They instinctively scurry quickly back downhill towards the water until they find sand wet and soft enough to re-bury themselves, waiting for the next wave. They lack the means to bite, claw, or pinch. Many sand fleas exhibit bioluminescense when handled or disturbed at night. Many fishermen catch them with a special metal mesh scoop and use them as live bait while surf fishing for ocean-going fish, including the pompano, speckled trout, whiting, and sea mullet [1]
http://images.google.com/imgres?img...=/images?q=mole+crab&svnum=10&um=1&hl=en&sa=N
Live Sand Fleas (Emerita analoga)
Sand fleas or mole crabs are great bait either live or frozen. These beach crabs are common in the Atlantic, Gulf, and Pacific oceans. Sand fleas are often considered the best bait for Pompano, Jacks, Strippers, Grunts, Redfish, Sheepshead, Croakers, Bluefish, and many more.
Fishing Tips: Most commercial fishermen prefer to use circle hooks (size #1). Insert the hook from the underside near where the end of the tail touches the body. Push the hook out the top of the shell. Also, a red bead at the top of the hook is said to be useful.
