The Crotalinæ, until recently regarded as a family (Crotalidæ, ‘pit-vipers’), stand at the head of the ophidian ranks as the “most specialized type of snake structure,” and exhibit the “highest efficiency of the venom apparatus.” They are viper-like serpents of moderate length—none exceeding, and few approaching eight feet—but thick, heavy, and extremely muscular. They are viviparous, and mainly terrestrial; but one, at least (the moccasin), is decidedly aquatic, and several in Central and South America are arboreal. In colors they vary adaptively to their haunts. All are more or less distinctly marked with darker spots and patterns of squarish form. The group is predominantly American, but several species inhabit the East Indies, some of them belonging to the American genera Ancistrodon and Lachesis. The latter includes more than half of the 60 or so species of pit-vipers recognized, and is mainly Neotropical. Among its species are the large and dangerous bushmaster and fer de lance (qq.v.). Among smaller genera one is Teleuraspis, a species of which (Schlegelli) is arboreal and often winds around the stems at the centre of banana bunches, where it sometimes fatally bites the first man to handle the fruit. None of these have rattles. The true rattlesnakes, then, are only those pit-vipers which belong to the genera Sistrurus (three species) and Crotalus (15 species), all of which, except two species of Crotalus in South America, belong to the Northern Continent.
| PATTERNS OF COLOR MARKINGS. |
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1, Common Eastern banded rattlesnake (Crotalus durissus); 2, Diamond rattlesnake (Crotalus adamanteus); 3, green rattlesnake (Crotalus lepidus); 4, plains rattler (Crotalus confluentus). |
The curious epidermal structure at the end of the tail consists of a tapering series of amber-colored horny flattened bells which are locked into one another. The oldest or terminal bell (the ‘button’) is in reality the horny covering of the tip of the tail which was not discarded when the skin was first molted. At each succeeding molt the tip is pushed out by the new skin, and so a ‘bell’ is added at the base with each new shedding of the remainder of the skin. Theoretically these bells ought to indicate the number of moltings, and the age of the snake; but wear and accident interrupt or break the set so often that the rule does not hold with any certainty.
| RATTLE OF A RATTLESNAKE. |
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1, Perfect rattle of a large banded rattlesnake; 2, longitudinal section of rattle; 3, separate segments of disjointed perfect rattle of Crotalus (side view): a, basal ‘joint’; b, button. |
When the serpent is excited in any way it vibrates its tail, which (unless the creature is moving) is then held upright in the centre of the coiled body, with the head erect and menacing before it. This vibration—which is indulged by many kinds of snakes under nervous excitement—produces a peculiar humming noise, which increases in intensity and pitch as the snake's alarm or anger and the speed of vibration are augmented, until it may sound like the droning of an angry bee. The origin of the rattle can only be guessed at. A tendency toward armature of the tail is apparent in several other genera of pit-vipers; and in Sistrurus the rattle is much less well developed than in Crotalus. Apart from being a mere expression of emotion, the rattle serves to warn away cattle that might tread upon it, or enemies that might wish to seize it. This warning is well understood among all the wild animals, but when antelopes and deer hear it they will often attack the reptile and cut it to pieces with their sharp hoofs. The rattle is also believed to be a useful means of calling the sexes together.
The poison apparatus, fangs (which are of the proteroglyphic type), and the manner and result of biting, are treated of under Snake. Here it needs only be said that, like the vipers generally, these snakes are sluggish and loth to bite when it can be avoided, or when they are not surprised into a sudden stroke. This disposition varies, however, with the weather, their hunger, the season (all are irritable when sloughing their skin), and it differs in various species. Even the smallest may cause a man serious illness and perhaps death if it succeeds in introducing much poison into a wound; while a fairly delivered bite from the larger ones is almost certain to prove fatal. Its enemies are mainly confined to a few of the larger colubrine snakes, as the blacksnake, king-snake, and the like; to the pronghorn, Western deer, and Southern peccaries. Against man the rattlesnakes can make feeble resistance. Domestic pigs kill and eat as many as they can find, and rarely suffer harm, because of the thickness of the skin and the layers of fat underneath it, which prevent the fangs from entering or carrying venom to the system. Hunting of rattlesnakes affords occasional profit to a few persons, who find a market for their skins and for the clear smooth oil yielded by their fat, which is esteemed by watchmakers and gunsmiths, and is in demand as a medicine among the ignorant.
The most common and well-known of the rattlesnakes is that one (Crotalus durissus) formerly abundant all over the East, from the White Mountains in New Hampshire, and Lake Superior in the North, to the borders of the dry plains.
