Now does it show the singular advantages of its ubiquitous mode of progression. Let a tiny fish, a smaller crustacean, or a soft mollusc pass within a reasonable distance, and the crab darts at it with a tigerlike energy, seldom failing to secure its prey. I have seen these crabs run after and catch the black flies that are so common upon the sand, and once saw a burrowing wasp (Odynerus) snapped up as it alighted on a bit of seaweed. Everyone who has walked along a sandy shore at evening is familiar with the shrimp-like sand-hoppers or sand-skippers (Talitrus) that leap about with such untiring energy, and the difficulty of capturing one of these active creatures. Yet I have seen the green crabs give chase to the sand-hoppers, and pounce on them as cats on mice.
The method employed in their capture of all active animals is rather unique. As soon as the crab sees the intended prey, it sits up for a moment, darts at the doomed being, and literally flings itself upon the victim, imprisoning it beneath the body, and hemming it in by means of the legs, which make an impassable cage around. One of the claws is then inserted under the body, and the prisoner picked daintily out as if by a dexterous thumb and finger. One claw then holds the prey, while the other pulls it to pieces and puts the morsels deftly into the mouth. The crab knows the value of time, and loses not a moment in disposing of its prey, tucking it into its voracious maw with amusing dispatch, and looking out the while for a fresh victim. Once I saw a very large sand-hopper make its escape from its pursuer. It gained nothing, however, but a temporary release, for the crab instantly gave chase, secured, and ate it in a few moments.
Fierce and destructive as it may be, the green crab is itself a frequent victim to more powerful foes, and is often doomed, with poetical justice, to undergo the sufferings which it has inflicted upon other beings. None are more terrible enemies than those of its own species, for the crab is an insatiate cannibal, devouring its kindred without the slightest compunction. In all these cases, however, it is needful that the dimensions of slain and slayer should be very disproportionate, as the crab cares not to earn a meal through a fight.
I was lately witness to a very amusing episode, where a large and powerful crab caught sight of a tender little one, as it scuttled over the wet sand. Away started the giant in full chase, and away ran the pigmy, as if knowing that life and death hung on the issue of the race. In spite of the great disproportion in size, the superior activity of the smaller crab prevented its pursuer from gaining much ground; but at last its strength evidently began to fail, and I thought it must inevitably succumb to the terrible foe that pressed so fiercely on its footsteps. Suddenly, however, it darted under a stem of laminaria that was lying on the shore, gathered all its limbs under its shell, and there lay motionless. The pursuer was instantly baffled. It raised itself in the air and surveyed the shore in all directions. Then it prowled about like a cat that has lost a mouse. It even was cunning enough to turn over some bits of seaweed that were lying on the shore, but never thought of searching under the thick stem of the laminaria. At last it gave up the pursuit, returned disconsolately to the sea, shovelled itself under the sand, and I saw it no more. Its intended victim then cautiously looked from its place of shelter, just protruded a claw, then a leg, then looked again, and at last came boldly forth, and went off to catch something on its own account.
As a general rule, the larger the size of the crab the more bellicose is its disposition. The smaller specimens are usually discreet as well as valorous, and if surprised either run away as fast as they can, or burrow into the sand with all speed. But the great, broad-shelled bully of the rocks has had his own way so long that his first impulse is always to show fight, and no sooner does he catch sight of the advancing foe than down goes his tail and up go his claws, and there he sits, defiantly ready for instant combat. It is as well to be cautious about handling such a champion, for he can strike with his claws as swiftly as a serpent darts its armed head, and should he miss his aim the clash of the bony weapons is distinctly audible.
Be it well understood that a bite from such a creature is no trifle, for the claws are enormously powerful, and their tips are sharply toothed, and they hold like the jaws of a bull-dog.
Even this belligerent animal is ofttimes fain to retreat before a foe of greater powers, stronger weapons, and harder shell, the edible crab which figures on our tables, and is known among the seaside population as the punger. Fortunately, however, for our green friend, the punger mostly inhabits a different belt of water, being most commonly found among the rocks at low-water mark, whereas the green crab lives almost wholly above that elevation.
Many persons when walking along the shore have observed a curious series of little marks on the sand, set in rows of five or so in depth, and meandering in seemingly purposeless irregularities. At first the marks appear to be made without any order, but a little examination will show that the same group of marks is repeated at regular intervals. These are the foot-tracks of the green crab, and the distance between the similar lines of marks denotes the size of the animal that made them.
Guided by these tracks, an experienced shore-haunter can often follow the crab to its place of concealment, and bring it to light, whether it be buried in the sand, or lying under the shelter of pendent seaweeds. In attempting this feat, however, it is as well to be quite sure of the direction in which the crab has gone, so as not to be led away from, instead of towards, the hidden crustacean. This object can always be attained by examining the shape of the marks, which are always larger at one end than the other, the larger extremities always pointing in the direction which the crab has taken.
There is much more to be said of these creatures, but failing space will not permit of further description. Should, however, any reader of these lines suffer the annoyance of a wet day at the sea-side, he is hereby recommended to procure a water-proof garment, to betake himself to the shore as the tide is rising, and amuse himself by watching the crabs.
