When I was a kid, we'd go to the beach and dig in the sand. We caught tiny crab-like creatures that scurried and dug burrows right at the edge of the surf. They never bit or pinched, and they were cute and fun to play with. We called them sand crabs.

After I'd grown up, I walked down different beaches and saw fishermen dragging cage-like metal contraptions across the sand. They dumped out their catch, which they called sand fleas, in buckets to use as bait for their hooks. These were the same tiny animals I'd dug up with my cousins years ago.

It turns out that these little crabs are crustaceans of genus Emerita. There seem to be several species dispersed across the world's beaches; two of the more common species are Emerita talpoida on the Atlantic coast of North America, and Emerita analoga on the Pacific shores. They're not true crabs, so to speak, since they walk backwards rather than sideways.

There doesn't seem to be a general consensus about what to call these things. Mole crab seems to be a common name for them, but this name is also used for several varieties of "real" crabs. The same problem exists for the name of sand crab. Sand flea might be good, but they're not really fleas, of course, and that name is used properly for certain blood-sucking insects that are.

Whatever you want to call them, they're exceedingly common on many sandy beaches. Moving up and down the beach to keep with the tide, they bury themselves in the sand and eat tiny flecks of organic material drifting in the water. They grow up to a few centimeters in length, depending on species, with females usually about twice the size of males.

The sand crab's compact body and tough outer shell protect it well from the constant tumbling action of the waves, but not from the multitude of birds and fish that eat it. Those I've seen are colored a nondescript beige and blend in well with the sand; I suppose this is true throughout the rest of the world as well. Their eggs are a bright and very noticeable orange, though.

Although I've never done any surf fishing, those that do unilaterally declare sand crabs (usually sand fleas in this context) to be excellent bait. It's an ideal situation, really - where else can you catch your bait (and know it's fresh) moments before casting your line? Fish apparently find them delicious enough that fishermen in areas where sand fleas are uncommon will sometimes buy sand flea extracts and other such concoctions to make their bait more appealing to the fish they're trying to catch.

Waves that wash up on the beach carry lots of things in them — sand, salt, plankton, bacteria, tiny fragments of rot.

California beaches have a rough beauty to them. The sand is dark and the ocean is green. People are all over the place even in the wintertime. Nothing like empty postcard beaches, with white sand and water shimmering blue like lapis — I've never seen a beach like that.

I have a point. I promise.

It's odd, the things that make you remember.

One summer I was on my knees with an old girlfriend at the edge of the Huntington Beach tide, noticing that there was sand stuck to her thighs. The sand was full of life and had been drawn up from dark ocean bottoms; it had once been part of a submerged mountain range, the shell of some ancient mollusc, a bone. We were clammy with the cold salt of the Pacific. When she smiled wet strands of her hair hung in her eyes and flashes of sunlight danced out of the ocean droplets on her skin. Countless treasures were shining with the salt water in the creases of our flesh. Things carried by the ocean. The ocean was beautiful but somehow it was even more beautiful shining on us. Ocean is the best sunblock. It doesn't work and isn't meant to be sunblock. But it's the best.

Sand crabs. We were there to find sand crabs. I thought about sand crabs this morning and remembered a lover's thighs and oceans full of life.

It's odd, the things that make you remember. That is my point.

Here is a writeup about sand crabs.

Emerita — the sand crab

Kingdom Animalia
Phylum Anthropoda
Subphylum Crustacea
Class Malacostraca
Order Decapoda
Suborder Pleocyemata
Infraorder Anomura
Superfamily Hippoidea
Family Hippidae
Genus Emerita

When you're at the beach, watch the sand closely after each wave recedes. You'll see what looks like an eruption of bubbles from inside the earth. That's sand crabs.

Sand crabs, also known as mole crabs, are among the smallest crabs around. They typically attain a length of 30 millimeters. They look like rocks and unlike most crabs don't have pincers. They live on the beach, literally, where the sand meets the surf.

They spend much of their lives submerged. They eat detrius and plankton. Food is captured with hairy feelers, extended to the surf. When full, the feelers are retracted into the body and scraped off. When the water recedes and pulls the earth out from around sand crabs they dig furiously to return to cover. You don't think of crabs as agile critters — especially these, because they're so stocky and awkward-looking — but sand crabs are quick. In the wake of a draining wave they disappear in a flash. You're never sure whether the twinkling light is rippling water or burrowing sand crabs.

During the reproductive season, female crabs can carry a clutch of eggs each month up to 45,000 strong. The eggs are bright orange and on a freshly fertilized crab look like mold. As the larvae consume the yolk the eggs turn darker and darker brown. Baby sand crabs are planktonic for several months after hatching.

Male and female sand crabs can be distinguished by pleopods, small legs used to hold the clump of eggs against the body. They are in three sets on the abdomen and look like white threads. Guess which sex has pleopods.

Catching

Most sand crabs are caught as bait for fishermen using drudge nets at the ends of long poles. The nets are used not only to obtain large quantities of crabs but to keep sand out from beneath the fingernails and to prevent the squirmy feeling of legs brushing against palms. This is useful but it is no fun: I'm going to assume you're not a fisherman.

You need to be on your knees, get close to the sand, get used to the chill of the ocean. Look for bubbles. Be quick but gentle — get your fingers into the sand while it's still soft. Try to scoop the crab up from underneath. If you chase it with your fingers you will lose every time. You'll learn quickly that these things are fast.

Once you have one, wash it off with the next wave. Look for pleopods. Look at the markings on the shell. Look at the wiggling legs. Look at the evolutionary engineering — this is an insignificant creature. Realize that no creature is insignificant.

If, while absorbed in the wonder of a sand crab, you are knocked into the sand by a surprise wave, you have accomplished your mission. Laugh and be happy and continue.

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Sources

Farallones
http://www.farallones.org/sandcrabs/history.asp

The Assateague Naturalist
http://www.assateague.com/mole-cr.html

Wikipedia
http://en.wikipedia.org/wiki/Sand_crab.html