Half Hours with the Lower Animals / Protozoans, Sponges, Corals, Shells, Insects, and Crustaceans

by Charles Frederick Holder

XVI. THE CRABS

Of all the crustaceans, the crabs are the most singular and certainly the most intelligent. Rapid in movement, good swimmers, alert, garbed in extraordinary colors, often in stolen homes, they attract attention at once and are the harlequins and clowns of the animal kingdom. The crabs are distinguished from the rest of the group principally by their very short tails. Their bodies are round, elongated, or oval. They are found almost everywhere, from the deep sea, where they occupy shells and sometimes drag about a luminous sea anemone, to every beach. It is in or near the tropics that the most remarkable crabs are seen.

During a visit to the islands off the coast of Texas, I once found a remarkable crab community. The islands were flat sand banks just above the surface, blown and washed up by the sea, with here and there sand dunes and shrubs, and again vast stretches of sand inhabited only by crabs. The latter were all of one kind, a pale gray, so mimicking the sand in color that it was almost impossible to distinguish one from the other. There were legions of them, the sand in places being fairly riddled with their burrows, into which they darted with inconceivable rapidity. As I walked along the sands they ran ahead in rapidly increasing numbers, then divided and were so quick of foot that it was impossible to run them down. This vast army of crabs was the sanitary corps of the island, devouring every dead fish that came ashore and other animal matter of all kinds.

Fig. 147.—A land crab Gecarcinus).

At Garden Key, Florida, these crabs were found in swarms, rarely entering the water except when driven, and never venturing far from the reach of the highest waves at high tide. They had long, stalked eyes, which seem to follow every movement, and were very comical and interesting creatures to watch and study. On the keys covered with bay cedars were other land crabs (Fig. 147), colored rich red and purple. These crabs lived among the cactuses and bay cedar bushes. When climbing on the former their resemblance in shape and color to the purple fruit was remarkable, and if the crab remained quiet, it was almost impossible to distinguish it. In these bushes a tern, the noddy, had built its rude brush nest, and the young bird and the food brought it by the parents were the objects of marked attention on the part of not only the purple-backed crab but a hungry, starving horde of hermit crabs which climbed the tree and snatched the bits of fish from the young birds, despite the presence of their mother. By crawling beneath the thick brush in heat which was almost suffocating, I watched numbers of these foraging expeditions on the part of the crabs, and I think it possible that some of the larger crabs finally carried off the young birds. This was not an impossible feat, as Professor Mosely, of the Challenger deep-sea dredging expedition, observed the same crab or a very near relative, carry off young birds at St. Paul's Rocks. At Ascension he saw the doughty land crabs stealing young rabbits, dragging them from their holes by main force and devouring them. This crab with gorgeous colors was not very fleet of foot, and when I rose up suddenly in the cactus by a nest they would draw in their legs and cling to a branch, mimicking ripe fruit. The hermits would do the same, and fall to the ground in a shower.

An interesting crab found here is known as Grapsus, also a predatory creature with unequaled courage, preying upon every living thing that it can attack with safety. It is richly colored red and white; its legs are long; it is a racer along the sands, impossible to capture. On the West African coast these crabs, or a near relative, are very large, and so swift that they have been used in sport, horsemen following them at full speed as game.

The ordinary crab of the Eastern shore is highly valued, and vast numbers are shipped from Fort Monroe in Virginia to the northern cities. The trade in "soft shells" is even more important. The latter are caught in various ways. An old colored man of my acquaintance used to tread for them on the mud flats with his bare feet; but he confessed that it was a disagreeable business, as sometimes he stepped on "hard shells" by mistake and was badly bitten.

The English edible crab is of large size and always in demand, resembling the edible crab of the Pacific, which is also very large and greatly esteemed.