Читать книгу: «Birds and Nature Vol. 9 No. 2 [February 1901]», страница 5

In another genus of Pupidae, Clausilia, nature has provided the aperture of the shell with a little valve called a “clausilium,” which acts as a spring door to close the shell against all its enemies. This door is an additional safeguard as the aperture is already provided with numerous teeth and folds. In this manner does Mother Nature look after her children.

It is a curious fact that in all the larger groups of animals there are one or more genera which have the cruel and bloodthirsty propensities of the shark. The Mollusca are no exception to this rule, and we find in the genus Testacella an animal having all the ferocious propensities of the terrible man-eating tiger. This mollusk has a long, worm-like body, the shell being very small and rudimentary, ear shaped, and placed on the extreme posterior end of the animal. Its principal food consists of earth-worms, although it will attack other mollusks and even its own species. It has been likened to the tiger and the shark in its cunning while pursuing its prey and in its ferocity when attacking it. The poor earth-worm stands but a slight chance of escape when Testacella scents it and starts in pursuit. The worm tries to escape by retreating into its underground galleries, but this is of no avail because the mollusk has a long, narrow body and can go wherever the worm does. If the worm, perchance, has the opportunity of retreating far into its galleries, the mollusk will dig tunnels to intercept it. Frequently the mollusk will make a sudden spring upon its victim, taking it by surprise. This slug-like snail will frequently devour a snail much larger than itself, but if the victim is too large for one meal it will be broken in the middle and one half eaten and digested and then the meal completed with the other half.

The Testacella also resembles the tiger and the shark in the possession of long, fang-like teeth upon its radula. These teeth are recurved and aid the mollusk in getting a firm hold upon its victim, and also assist in the operation of swallowing. It is a curious fact that this animal will not feed upon other dead animals nor upon fresh meat, nor freshly-killed worms. Like the snake, which it greatly resembles in habits, it must hunt and kill its own food. Its wanderings are nocturnal and during the day it remains concealed, buried in the earth. Testacella is quite long lived, as snails go, its duration of life being about six years.

A genus allied to Testacella, and having the same predaceous habits, but being protected by a large shell into which the whole animal can withdraw, is the Oleacina or Glandina. The shell is long, with a narrow aperture and a dome-shaped spire; the animal is long and narrow and the head near the mouth is furnished with a pair of elongated lips which may be used as tentacles. The South American species feed on the larger mollusks, as the Bulimus before spoken of, and the aperture of each intended victim’s shell is carefully examined before any attempt is made to enter. When our “tiger” is satisfied that its victim is really within, it will enter the aperture and devour the animal. Sometimes it will make a hole for itself in the shell of its victim and will eat the contents through this aperture instead of the natural one. In Florida these animals prey upon the large pulmonates like Lignus and Orthalicus.

Before closing this brief sketch of the Land Mollusks we must not neglect to mention their wonderful protection against the cold of winter and the heat of summer. This is a tough, leathery secretion, which completely covers the aperture, and its formation is thus described by Mr. W. G. Binney in his “Manual of American Land Shells.”

“Withdrawing into the shell, it forms over the aperture a membraneous covering, consisting of a thin, semi-transparent mixture of lime, mucus or gelatine, secreted from the collar of the animal. This membrane is called the epiphragm. It is formed in this manner: The animal being withdrawn into the shell, the collar is brought to a level with the aperture, and a quantity of mucus is poured out from it and covers it. A small quantity of air is then emitted from the respiratory foramen, which detaches the mucus from the surface of the collar, and projects it in a convex form, like a bubble. At the same moment the animal retreats farther into the shell, leaving a vacuum between itself and the membrane, which is consequently pressed back by the external air to a level with the aperture, or even farther, so as to form a concave surface, where, having become desiccated and hard, it remains fixed. These operations are nearly simultaneous and occupy but an instant. As the weather becomes colder the animal retires farther into the shell, and makes another septum, and so on, until there are sometimes as many as six of these partitions.”

The air-breathing snails which we have so briefly discussed in this article, are but a very limited number of the many thousand species of this very interesting group of animals. Their shells are easily gathered and require but little trouble to prepare for the cabinet and for study. The writer, therefore, trusts that what has been written may act as a stimulus and induce many to take up the collection and study of these beautiful objects.

Frank Collins Baker.

THE GILA MONSTER
(Heloderma suspectum.)

The reptile fauna of the North American continent includes a curious lizard known as Gila Monster, in science called Heloderma. It represents a family all to itself, with only two species: Heloderma horridum and Heloderma suspectum.

Francisco Hernandez, a Spanish physician and naturalist, was the first to know of its existence when he found it in Mexico in the year 1651. In an account of his explorations he mentions a lizard three feet long, with a thick-set body, covered with wart-like skin, gaudily colored in orange and black, and generally of such horrid appearance that Wiegmann, another scientist, two hundred years later, called it Heloderma horridum.

For a long time this name was given indiscriminately to all lizards of this kind, living either south or north of the boundary line of Mexico and the United States, till Professor Cope discovered a difference between them and called the variety found in our southwestern territories and states Heloderma suspectum.

Many other naturalists have since taken up the study of this interesting reptile. The result of their observations and experiments was that they all agree in acknowledging the Heloderma as the only poisonous lizard in existence, although their opinions are at variance as to the effect of its venom on the human system. Dr. van Denburgh in his latest researches has found two glands, one on each side of the lower jaw, located between the skin and the bone. Such a venom-producing gland being taken out of its enveloping membrane proves to be not a single body, but an agglomeration of several small ones, differing in size, and each emptying through a separate duct. These glands are not directly communicated to the teeth. When the animal is highly irritated, caused by constant teasing or rough handling or by being trodden upon, the poison is emitted by the glands, gathers on the floor of the mouth, where it mixes with the saliva, and is transmitted through the bite.

A Heloderma has no fangs, but a goodly number of sharp, pointed teeth, both on the upper and lower jaws. They are curved backward and about an eighth of an inch long, or even less than that. The principal characteristic of these teeth is that they are grooved, facilitating thus the flow of the venom into the wound. It bites with an extremely swift dash, directed sideways, and holds on tenaciously to whatever is seized with its powerful jaws. Sumichrast says when the reptile bites it throws itself on its back, but none of the later naturalists makes mention of this peculiarity.

The venom of the Gila Monster injected into the veins and arteries of smaller animals as rats, cavies and rabbits and into the breast of pigeons and chickens, causes death within twenty seconds to seven minutes. Brehm relates that a young Heloderma, and in poor physical condition besides, was induced to bite the leg of a large, well-fed cat, which did not die, but gave signs of prolonged terrible sufferings. It became dull and emaciated and never regained its former good spirits.

Among several cases of Gila Monster bites inflicted on human beings can be quoted that of Dr. Shufeldt, who, in “The American Naturalist,” gave an interesting account of the sensations he experienced. It is sufficient to say that the pain, starting from a wound on the right thumb, went like an electric shock through the whole body and was so severe as to cause the victim to faint. Immediate treatment prevented more serious consequences. The Doctor, nevertheless, was a very sick man for several days and began to recover only after a week had elapsed.

The constituents of the venom are as yet not thoroughly known, but it is said to be of an alkaline nature, the opposite of snake poison, which is acid. It acts upon the heart, the spine and the nerve centers and causes paralysis.

Other scientists claim the saliva of the Heloderma is poisonous only in certain cases and under certain circumstances. It may also depend upon the physical condition of the victim at the time the venom enters into the system. Yet there is little doubt that, if help is not at hand immediately, the bite may prove fatal.

The Apaches stand in dire fear of this animal, so that, at least, with their older people no amount of money seems tempting enough to make them go near it, much less to capture one. A former resident of the territories says both Indians and Mexicans believe firmly that if a Gila Monster only breathes in your face it is quite sufficient to cause immediate death. On an old Indian trail, a good day’s journey west from the present site of Phoenix, can be found, crudely outlined on the face of a rock, the picture of two Helodermas pursuing a man who runs to save his life. Numerous hieroglyphic inscriptions tell probably the story of the event and prove not only the prehistoric origin of this primitive piece of art, but also the erroneous ideas which were prevalent in these remote times, for the reptile never attacks and never pursues. It is safe to say that the animal has been vastly misrepresented at all ages.

Nature has kindly provided the Heloderma with a compensation for its partially undeserved bad reputation in giving it beauty. For whosoever looks upon a fine specimen with unprejudiced eyes cannot fail to admire at least the combination of its colors and especially the odd, capriciously disposed markings; the delicately tinted skin, studded in transverse rows with shiny tubercles, like so many beads on strings.

The illustration to this paper is so excellently made that scarcely any description is necessary as to the animal’s exterior in color and markings. This Heloderma is a little over nineteen inches in length by ten inches in circumference of the body and five inches at the thickest part of the tail, which makes one-third of the total length of the body. When such a reptile grows to the size of eighteen inches it is called adult. Those growing beyond these figures are unusually large specimens and in very rare instances the species of our illustration reaches the extraordinary length of two feet. An adult Gila Monster weighs about two or three pounds, and in winter less than in summer.

The four short and stubby legs seem quite out of proportion to the massive body, much more so as the two pairs are widely separated lengthwise of the body. When walking the body is elevated, while in rest it lies flat on the ground. Each foot is provided with five digits armed with curved white claws.

The skin has generally the appearance as if covered with rows of uniform beads; but, on closer examination, these beads, or more correctly, tubercles, prove to have different shapes and are differently set, according to the part of the body which they cover. On the head from the nose up to between the eyes they are flat, irregularly cut, closely joined and adhere completely to the skull. Those following form polygonal eminences, each one separated from the other by a circle of tiny dermal granulations, while behind the eyes on both sides of the head they are larger, semi-spherical and stand far apart. The throat and the nape of the neck are studded with very closely set small tubercles, increasing in size only above the forelegs, whence they extend in well-defined, transverse rows along the whole upper side of the body and the tail. The under side of the latter and the abdomen are covered with tessellated scales of a light-brown and dull yellow color arranged in another handsome pattern.

A Heloderma’s head, with its triangular shape, is very like that of a venomous snake; it gives the animal – especially when it is raised in anger – a truly awe-inspiring appearance.

The wide-cleft mouth reaches far behind the eyes. These are very small and, like all lizards, provided with eye-lids that close when the animal sleeps. The eye itself has a dark-brown iris, with the round pupil that indicates diurnal or at least semi-nocturnal habits. Between the nostrils, well in front of the blunt nose, is a wide space. The nostrils are so far down as to nearly touch the margin of the supra-labial scales. This position denotes terrestrial habits in reptiles rather than an all aquatic life. For to most of them water is indispensable to their welfare. Thus the Gila Monster shows this structure as it likes to bathe in shallow water, often for many hours at a time.

The crescent-shaped openings of the ears are situated not far from the edge of the mouth, between the head and the neck, and are partly concealed and also protected by the overlapping gular fold; the tympanum is exposed. The animal sees and hears well. The remaining three senses are more or less concentrated in the tongue which is one of the most remarkable features of the Heloderma. It is slightly forked at the tips, half an inch wide and two to three inches long; it is dark reddish-brown with a shade of purple. When in rest it is drawn together into a small, conical shaped mass, scarcely an inch in length. But as soon as something disturbs the usual quietude of the animal the tongue is thrown out immediately. In fact, it is used for smelling, tasting, feeling. It is used for measuring depth and distance, for expressing desire and satisfaction; and with what rapidity is this instrument of communication projected and retracted!

A Gila Monster may be trusted to some extent as long as the tongue is freely used, but if that is not the case it is wise to be careful in handling it. Fear and hostility are expressed by deep, long-drawn hisses; by opening the mouth to its fullest extent and by quick jerks of the head from one side to the other.

At the present time these reptiles are not so very common. Ever-prevailing superstition among the ignorant and exaggerated bad reputation have brought on a relentless war of extermination against them, so that now in the neighborhood of settlements they are seen seldom if ever. Their center of distribution is more and more confined to the region along the banks of the Gila river in Arizona, although less frequently they may still be found as far west as the Mojave desert in California. But those are wrong who believe that the Heloderma is living only in the most arid portions of the southwest. There are several reasons why the reptile seeks eagerly irrigated places, which are productive of some vegetation, for it needs water, food and shady hiding-places.

In the middle of summer, when even the larger streams are dried up, the Gila Monster retires to some burrow, abandoned by another animal, or to deep crevices in the rocks, and spends there in a torpid state several weeks, until the great rainfalls relieve the country, give fresh plant life and fill again the barren riverbeds. This is the animal’s summer retreat. During the course of a year it takes a second and longer one, the regular hibernation, that lasts about from November to the middle of February, when it resumes its outside life again. It loves to bask in the still mild rays of the sun, but as soon as the heat increases the Gila Monster seeks shelter for the day behind stones and bowlders, under clumps of cacti and in small mesquite groves along the river banks. It roams about only after sunset or early in the morning. The idea that this lizard enjoys the quivering heat on an open Arizona plain, while other sun and heat-loving reptiles keep in hiding, is as erroneous as many others. Nothing is so absolutely fatal to the Heloderma as to be exposed only for half an hour to the direct rays of the sun in midsummer. Another reason why it prefers to live in the neighborhood of streams where plant life is more abundant explains itself by the necessity to provide for food.

Whoever has an opportunity to observe reptiles in confinement for an extended period of time can easily draw conclusions as to their mode of living in freedom. A captive Gila Monster is fed on hens’ eggs; in summer one each week, in winter one every two or three weeks. It refuses every other kind of food, however temptingly it may be offered, such as mice, frogs, angleworms, mealworms and the like. It is more than probable that in their wild state they live on a similar diet, consisting then of eggs of other lizards, of turtles and of birds. The animal has the reputation of being destructive to the Arizona quail.

Several writers of Natural History add to this a diet of insects, but the embarrassed locomotion of the Heloderma seems to exclude flying and fast-running prey. Nearly all reptiles which feed on eggs climb, as do some snakes, and as does the slow and clumsy Gila Monster. They are not able to ascend high and straight trees, which, however, are not found in these regions, but they are able to climb bushes and low trees, having somewhat leaning trunks and rough bark. And it is wonderful to see how cleverly it disposes of the sharp claws and the muscular, half-prehensile tail, both in dragging itself up and in retarding an often too rapid descent.

The inquiry may be made: How is it possible that a Heloderma lives on eggs alone when it can find them only during the relatively short time of five or six months? First, it may be remembered that this period corresponds nearly to the active life of the animal before and after estivation. The second and more important reason is its remarkable frugality. The digestive organs are so constructed that they adapt themselves to a fast of many months without injury to the animal.

In captivity the Gila Monster begins to slough about January and continues this process during several months. The epidermis comes off not like a snake’s, in a whole piece, but in several, or more frequently in many, fragments.

There is still a wide field open for accurate observation and definite knowledge that we relinquish to the professional naturalist and to those fortunate ones who can study the animal in freedom.

Amelia Walson.

[Editor’s Note: The Gila Monster of the illustration is still living and has for some years been the interesting pet of one whose love of nature in all forms has found beauty in the reptile usually shunned alike by the savage and by civilized man.]