Читать книгу Intelligence in Plants and Animals - Thomas G. Gentry - Страница 12

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Among our first acquaintances of the sea-shore are sure to be a number of merry little sprites which do not seem to have yet mastered the lesson of walking straight ahead. Their movements will be seen to be in a direction at right angles to that towards which the head points. It is a very interesting sight to watch these apparently one-sided creatures hurrying off in their lateral progression towards their burrows in the sand or mud, or in quest of food. Pass them, and you will be surprised to see how quickly some of them will reverse their motion, seemingly without so much as pausing to glance at their pursuer, their machinery appearing to have given out at one end, thus compelling them to reverse and travel back over their old courses.

These little Fiddler- or Calling-crabs, as they are termed, are the most pronounced offenders against the commonly accepted rule of proper walking. Scattered all over the salt marshes and mud-flats, at about high-water mark, may be noted their burrows, which are about as large as a thrust made by an umbrella point, and from which can be frequently seen the little animal peeping forth, preparatory to making a sally. At another part of the flat, where the noise of your footsteps has not given signals of danger, hundreds of crabblings are busy with their out-door occupations. Draw near to them, and away they scamper to their dwellings, males and females intermingled promiscuously, the former recognizable by the undue development of one of the claws, which is carried transversely in front of the head. When the animal is provoked, this claw is brandished in a somewhat menacing manner, which has been likened by some to the pulling of a violin bow, and by others to the action of beckoning or calling, and hence the names which have been applied to these eccentric creatures.

Have you a desire for a more intimate knowledge of the animal, take him up by the big claw, and you can now examine him without the least fear of incurring the proofs of his displeasure. Two bead-like, compound eyes, supported on long stalks, which can be readily withdrawn into the protecting shield of the carapace, will be observed. From the manner of this support, which allows of vision in almost every direction, the name of stalk-eyed crustaceans has been given to the group in which this structure is found. The two pairs of feelers, which you see in front of the eyes, are known as antennæ and antennules. They are of peculiar interest, for, aside from acting as feelers, they subserve the functions of smelling and hearing, the auditory apparatus being lodged in the base of the smaller pair. There are ten feet, and this is a character of importance, as it is a feature distinctive of the ten-footed, or decapod, crustaceans. At first sight it appears that the animal is devoid of a tail, but if you turn him over upon his back you will find a very short one tucked safely under the body. A comparison of our study of this crab with that of the lobster or cray-fish will show that the tail, or, more properly, the abdomen, is stretched out beyond the body proper, and that the elongation is in proportion to the length of the animal. Two distinct groups of ten-legged, stalk-eyed crustaceans are thus recognized, namely: the short-tailed forms, or crabs, and the opposite, or long-tailed forms, to which the lobster and shrimp belong, the hermit-crabs constituting an intermediate type.

Two species of the Fiddler, considerably resembling each other in color and ornamentation, are to be found upon our Atlantic Coast. The more common form, Gelasimus vocator, has a smooth, shining carapace, while that of Gelasimus minax is finely granulated and in part tuberculated, the back of both appearing impressed with a figure very similar to the letter H. The latter, which appears to be a vegetable feeder, is the larger, its burrows not infrequently measuring one and a half inches in diameter. Estuarine regions, in close proximity to fresh water, rather than the tidal flats, are its habitat, and, in truth, it seems to be able to get along for weeks, and even months, without any absolute need of salt water.

FIDDLER-CRABS.

Two Males Fighting for a Female.

In the excavation of their homes the Fiddlers throw up the pellets of moist earth by means of their anterior walking legs, depositing their burden usually at some little distance from the mouth of the burrow. As winter approaches, the domiciliary apertures are closed up, and the famine of winter is spent in a state of torpidity.

With the advent of spring they come forth from their brumal retreats, and soon concern themselves with the duties incident to the propagation of their kind. Two males are often observed contending in the fiercest manner for the possession of a female. They strike with the formidable claw most powerful blows, and I have often seen an opponent so completely claw-locked as to be unutterly unable to make any determined resistance. These contests last a long while, and finally conclude with the complete vanquishment of one or the other of the fighting parties, one or both sustaining at times some severe injury as the loss of an eye-peduncle or the joint of a limb. All the while the battle is waging, the female is a silent, passive spectator, and generally allies herself with the successful competitor for her affections. Even during the summer season, when the cares of brood-raising no longer command and enslave the attention of the female, these combats are still indulged in by the males, growing out of, as it would seem, the lingering smarts of old animosities festering in the memory. While these carcinological lords of the sea-side are eminently fitted for the sparring business, the whole physiognomy of their smaller, weaker partners bespeaks a life in which broils can have no part, a life devoted to peaceful and domestic pursuits.

Differing widely in structure and habits from the Calling-crabs, and affecting watery situations near the shore, are to be found the Hermit-crabs. These sprightly little animals, which are usually of small size, and have truly habits of their own, that stamp them at once as being original and distinctive, are a source of never-failing delight to the student of nature. They derive their name, as is well known, from the seclusion into which they cast themselves as the inhabitants of the shells of other animals, but it is probably not generally known, however, that the rights of tenantry are oftentimes exercised in the most arbitrary manner. Not always satisfied with a dead shell, the Hermit-crab has been seen to raid upon a living possessor and attempt to drag him from his home, in which operation the assailant is often assisted by a number of his fellows, each bearing with him his castle as defensive armor. True, the attack is probably made in many instances for the purpose of getting possession of the enemy as well as his belongings, and, however this may be, forcible possession is by them considered no misdemeanor.

The body of the Hermit-crab, in the greater number of species, is unprovided with a carapace, and, being soft and liable to injury, the animal is compelled to seek shelter usually in a snail-shell, winding himself about the coils, to the inner extremity of which he attaches himself by his modified posterior feet. So securely is he now intrenched that it is only with difficulty he can be withdrawn, retracting himself as he does further and further within cover of the shell. A sudden fracture of the apex of the shell, under which appears to be the most delicate part of the animal’s body, will generally effect a speedy dislodgment, the frightened Crab dropping from the aperture.

With his progressive development in size the Hermit requires frequent changes of abode. His methods in securing a new habitation are among the most interesting of his life. He is very circumspect in his movements, and will make several reconnoissances before he is fully satisfied with the conditions of his prospective home, retiring after each visit to the old shell.

CRAB WAITING FOR FOOD UNDER A ROCK.

From a photograph taken through water.

Like many bipeds, he has his first of May, and so he goes house-hunting. He finds a shell. Will it do? He examines it within, feelingly if not courteously, to see whether it is to let. Satisfied on this point, he turns it over, then turns it round, to know if it will suit, the weight of the house being quite an item in the reckoning to one who is to carry it upon his back. All things being right, his mind is made up to move, and quickly, too, at that, lest he miss his chance through some more active fellow house-hunter who is on the alert. Out comes the body from the old house, and pop it goes into the new. The resolution to move, the surrender of the old house, and the occupancy of the new, were all effected within a fraction of a second of time.

WARTY HERMIT-CRABS.

One at Home, the Other House-Hunting.

But the matter does not always go on pleasantly. Two house-hunters may find the same tenement. Should they both desire it, then comes the tug of war. Dwell together they neither can nor will. Recourse is had to battle, in which the stronger proves his claim right by the rule of might. In these encounters terrible mutilations quite often occur.

As an offset to all this bad feeling and bloodshed, it is a sad sight to see the little Hermit when his time comes to die. However droll his career may have been, he is now very grave, for he knows he must part with life and all its joys and pleasures. Who can explain the strange fact? The poor little fellow comes out of his house to die. Yes, to die. To us humans home is the only fit place to die in, but to Eupagurus it has no attractions at this solemn time. Poor fellow! With a sad look and a melancholy movement he quits of his own will the house for which he fought so well. Those feelers that often stood out so provokingly, and that were quite as often poked into everybody’s business, now lie prone and harmless; the eyes have lost their pertness, and dead, stone dead, the houseless Hermit lies upon that moss-covered rock.

There are two species of Hermit-crab occurring on our coast, which are readily distinguishable from each other by their size and the difference in the shape of the big claw. Eupagurus pollicaris, the Warty Hermit, is the larger species. He inhabits the shells of the big Naticas and the Fulgurs, and can be easily recognized by his coarse, broad claws, which close up in great part the aperture of the shell which he occupies. In the more common form, Eupagurus longicarpus, which seldom attains a length exceeding an inch, the legs are all much elongated, giving the animal a very slender appearance.