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The feigning of death by certain animals for the purpose of deceiving their enemies, and thus securing immunity, is one of the greatest of the many evidences of intelligent action on their part. Letisimulation (from letum, death, and simulare, to feign) is not confined to any particular family, order, or species of animals, but exists in many, from the very lowest to the highest. The habit of feigning death has introduced a figure of speech in the English language, and has done much to magnify and perpetuate the fame of the only marsupial found outside of Australasia and the Malayan Archipelago. “Playing ’possum” is now a synonym for certain kinds of deception. Man himself has known this to be an efficacious stratagem on many occasions. I have only to recall the numerous instances related by hunters who have feigned death, and have then been abandoned by the animals attacking them. I have seen this habit in some of the lowest animals known to science. Some time ago, while examining the inhabitants of a drop of pond water under a high-power lens, I noticed several rhizopods busily feeding on the minute buds of an alga. These rhizopods suddenly drew in their hair-like cilia and sank to the bottom, to all appearances dead. I soon discovered the cause in the presence of a water-louse, an animal which feeds on these animalcules. It likewise sank to the bottom, and, after examining the rhizopods, swam away, evidently regarding them as dead and unfit for food. The rhizopods remained quiet for several seconds, and then swam to the alga and resumed feeding. This was not an accidental occurrence, for several times since I have been fortunate enough to witness the same wonderful performance. There were other minute animals swimming in the drop of water, but the rhizopods fed on unconcernedly until the shark of this microscopic sea appeared. They then recognized their danger at once, and used the only means in their power to escape. Through the agency of what sense did these little creatures discover the approach of their enemies? Is it possible that they and other like microscopic animals have eyes and ears so exceedingly small that lenses of the very highest power cannot make them visible? Or are they possessors of senses utterly unknown to and incapable of being appreciated by man? Science can neither affirm nor deny either of these suppositions. The fact alone remains that, through some sense, they discovered the presence of the enemy, and feigned death in order to escape.

There is a small fresh-water annelid which practises letisimulation when approached by the giant water-beetle. This annelid, when swimming, is a slender, graceful little creature, about one-eighth of an inch long, and as thick as a human hair; but when a water-beetle draws near, it stops swimming, relaxes its body, and hangs in the water like a bit of cotton thread. It has a twofold object in this: in the first place, it hopes that its enemy will think it a piece of wood fibre, bleached alga, or other non-edible substance; in the second place, if the beetle be not deceived, it will nevertheless consider it dead and unfit for food. I do not mean to say that this process of ratiocination really occurs in the annelid; its intelligence goes no farther, probably, than conscious determination. In the beetle, however, conscious determination is merged into intelligent ideation, for its actions in the premises are self-elective and selective.

Letisimulation in this animal is by no means infrequent, for I have seen it feign death repeatedly. Any one may observe this stratagem if he be provided with a glass of clear water, a dyticus, and several of these little worms. The annelid is able to distinguish the beetle when it is several inches distant, and the change from an animated worm to a seemingly lifeless thread is startling in its exceeding rapidity.

Even an anemone, a creature of very low organization indeed, has acquired this habit. On one occasion, near St. John’s, Newfoundland, I noticed a beautiful anemone in a pool of sea-water. I reached down my hand for it, when, presto! it shrivelled and shrunk like a flash into an unsightly green lump, and appeared nothing more than a moss-covered nodule of rock.

Very many grubs make use of this habit when they imagine themselves in danger. For instance, the “fever worm,” the larva of one of our common moths, the Isabella tiger-moth, is a noted death-feigner, and will “pretend dead” on the slightest provocation. Touch this grub with the toe of your boot, or with the tip of your finger, or with a stick, and it will at once curl up, to all appearances absolutely without life.

A gentleman recently told me that he saw the following example of letisimulation: One day, while sitting in his front yard, he saw a caterpillar crawling on the ground at his feet. The grub crawled too near the edge of a little pit in the sandy loam, and fell over, dragging with it a miniature avalanche of sand. It immediately essayed to climb up the north side of the pit, and had almost reached the top, when the treacherous soil gave way beneath its feet, and it rolled to the bottom. It then tried the west side, and met with a similar mishap. Not discouraged in the least by its failure, it then tried the east side, and reached the very edge, when it accidentally disturbed the equilibrium of a corncob poised upon the margin of the pit, dislodged it, and fell with it to the bottom. The caterpillar evidently thought the cob was an enemy, for it at once rolled itself into a ball and feigned death. It remained quiescent for some time, but finally “came to life,” tried the south side with triumphant success, and went on its way rejoicing. This little creature evinced conscious determination and a certain amount of reason; for it never tried the same side of the pit in its endeavors to escape, but always essayed a different side from that where it had encountered failure.

Many free-swimming rotifers practise letisimulation when disturbed or when threatened by what they consider impending danger. If a “pitcher rotifer” (Brachionus urceolaris) be approached with a needle point, it will cease all motion and sink; the same is true of the “skeleton rotifer” (Dinocharis pocillum) and numerous others of this large family. Again, if a bit of alga on which there is a colony of “bell animalcules” (Vorticellae) be placed in a live box and then be examined with a moderate power, they can be seen to feign death. The rapidly vibrating cilia which surround the margin of the “bells” give rise to currents in the water which can be easily made out as they sweep floating particles toward the creatures’ mouths and stomachs. If the table on which the microscope rests be rapped with the knuckles, the colony will disappear as if by magic. Now, what has become of it? If the microscope be readjusted, a group of tubercles will be observed on the alga; these are the vorticellae. They have simply coiled themselves upon their slender stems, have drawn in their cilia, and are feigning death. In a few seconds one, and then another, will erect its stem; finally, the entire colony will “come to life” and resume feeding until they are again frightened, when they will at once resort to letisimulation.

Death-feigners are found in four divisions of animal life; viz., among insects, birds, mammals, and reptiles. Indeed, the most gifted letisimulants in the entire animal kingdom are to be observed in the great snake family. The so-called “black viper” of the middle United States is the most accomplished death-feigner that I have ever seen; its make-believe death struggles, in which it writhes and twists in seeming agony and finally turns upon its back and assumes rigor mortis, cannot be surpassed by any actor “on the boards” in point of pantomimic excellence.

I do not know of any fish which has acquired this strategic habit, but the evidence is not all in, and some day, perhaps, death-feigners may be found even among fishes.

Recently, I saw this stratagem perpetrated by a creature so low in the scale of animal life, and living amid surroundings so free from ordinary dangers, that, at first, I was loath to credit the evidence of my own perceptive powers; and it was only after long-continued observation that I was finally convinced that it was really an instance of letisimulation.

The animal in question was the itch mite (Sarcoptes hominis), which is frequently met with by physicians in practice, but which is rarely seen, although it is very often felt, by mankind, especially by those unfortunates who are forced by circumstances to dwell amid squalid and filthy surroundings. Sarcoptes hominis is eminently a creature of filth, and is primarily a scavenger living on the dead and cast-off products of the skin. It is only when the desire for perpetuating its race seizes it that it burrows into the skin, thereby producing the intolerable itching which has given to it its very appropriate name. It is only the females that make tunnels in the skin; the males move freely over the surface of the epidermis. The females make tunnels or cuniculi in the cuticle, in which they lay their eggs, and they can readily be removed from these burrows with a needle. While observing one of these minute acarii through a pocket lens, as it crawled slowly on the surface of the skin, I wished to examine the under surface of its body. When I touched it with the point of a needle in attempting to turn it upon its back, it at once ceased to crawl and drew in its short, turtle-like legs toward its sides. It remained absolutely without motion for several seconds, and then slowly resumed its march. Again I touched it, and again it came to a halt, and took up its onward march only after several seconds had elapsed. Again and again I performed this experiment with like results; finally, the little traveller became thoroughly chilled, and, after a fruitless endeavor to again penetrate the skin, ceased all motion and died.

Many of the coleoptera are good letisimulants. The common tumble-bug (Canthon laevis), which may be seen any day in August rolling its ball of manure, in which are its eggs, to some suitable place of interment, is a remarkable death-feigner. Touch it, and at once it falls over, apparently dead. It draws in its legs, which become stiff and rigid; even its antennæ are motionless. You may pick it up and examine it closely; it will not give the slightest sign of life. Place it on the ground and retire a little from it, and, in a few moments, you will see it erect one of its antennæ and then the other. Its ears are in its antennæ, and it is listening for dangerous sounds. Move your foot or stamp upon the ground, and back they go, and the beetle again becomes seemingly moribund.

This you may do several times, but the little animal, soon discovering that the sounds you make are not indicative of peril to it, scrambles to its feet and resumes the rolling of its precious ball. The habit of making use of this subterfuge is undoubtedly instinctive in this creature; but the line of action governing the use of the stratagem is evidently suggested by intelligent, correlated ideation.

Some animals feign death after exhausting all other means of defence. The stink-bug (pentatomid) or bombardier bug (not the “bombardier beetle”) has, on the sides of its abdomen near its middle coxae ("hip bone"), certain bladder-like glands which secrete an acrid, foul-smelling fluid; it has the power of ejecting this fluid at will.

When approached by an enemy, the stink-bug presents one side to the foe, crouching down on the opposite side, thus elevating its battery, and waits until its molester is within range; it then fires its broadside at the enemy. If the foe is not vanquished (as it commonly is), but still continues the attack, the bombardier turns and fires another broadside from the opposite side. If this second discharge does not prove efficacious (and I have rarely known it to fail), the little insect topples over, draws in its legs, and pretends to be dead.

Many a man has acted in like manner. He has fought as long as he could; then, seeing the odds against him, he has feigned death, hoping that his antagonist would abandon him and cease his onslaughts. The stink-bug in this seems to be governed and directed by reason, though the means used for defence must come under the head of instinct. Many a blind, instinctive impulse in the lower animals is, in all probability, aided and abetted by intelligent ratiocination when once it has made its appearance.

I have seen ants execute a like stratagem when overcome either by numbers or by stronger ants. They curl up their legs, draw down their antennæ, and drop to the ground. They will allow themselves to be pulled about by their foes without the slightest resistance, showing no signs of life whatever. The enemy soon leaves them, whereupon the cunning little creatures take to their feet and hurry away.

The most noted and best known letisimulant among mammals is the opossum. I have seen this animal look as if dead for hours at a time. It can be thrown down any way, and its body and limbs will remain in the position assigned to them by gravity. It presents a perfect picture of death. The hare will act in the same way on occasions. The cat has been seen to feign death for the purpose of enticing its prey within grasping distance of its paws. In the mountains of East Tennessee (Chilhowee) I once saw a hound which would “play dead” when attacked by a more powerful dog than itself. It would fall upon its back, close its eyes, open its mouth, and loll out its tongue. Its antagonist would appear nonplussed at such strange conduct, and would soon leave it alone. Its master declared that it had not been taught the trick by man, but that the habit was inherited or learned from its mother, which practised the same deception when hard pushed.

Most animals are slain for food by other animals. There is a continual struggle for existence. The carnivora and insectivora, with certain exceptions, prefer freshly killed food. They will not touch tainted meat when they can procure the recently killed, blood-filled bodies of their prey. The exigencies of their surroundings in their struggle for existence, however, often compel them to eat carrion.

Dogs will occasionally eat carrion, but sparingly, and apparently as a relish, just as we sometimes eat odoriferous and putrid cheeses, and the Turks, assafoetida.

Carnivora and insectivora would much prefer to do their own butchery; hence, when they come upon their prey apparently dead, they will leave it alone and go in search of other quarry, unless they are very hungry.

Tainted flesh is a dangerous substance to go into any stomach, unless it be that of a buzzard. Heredity and environment have made this bird a carrion-eater, hence, like the jackal, the hyena, and the alligator, companion scavengers, it can eat putrid flesh with impunity. Other flesh-eating animals avoid carrion when they can, for long years of experience have taught them that decaying meat contains certain ptomaïnes which render it very poisonous; hence, they let dead, or seemingly dead, creatures severely alone. Again, these creatures can see no object in mutilating an animal which, in their opinion, is already dead.

In this discussion of the means and methods of protection that are to be observed in the lower animals, I have brought forward only those in which mind-element was to be discerned. Mimicry and kindred phenomena hardly have a place in this treatise, for they are, undoubtedly, governed and directed by unconscious mind, a psychical phase which, as I intimated in the introductory chapter of this book, would be discussed only incidentally.