Nature's Teachings: Human Invention Anticipated by Nature. J. G. WoodЧитать онлайн книгу.
They are evidently borrowed from actual jaws, the same words being used to signify the movable portions and notches of the trap as are employed to designate the corresponding parts in the real jaw.
In both figures of the accompanying illustration we shall see how exact is the parallel. On the right hand is a common rat-trap, or gin, such as is sold for eightpence, with the jaws wide open, so as to show the teeth. On the left is a sketch of the upper and lower jaws of the Dolphin, in which an exactly analogous structure is to be seen.
The figure on the right hand of the lower illustration shows a man-trap as it appears when closed, the teeth interlocking so as exactly to fit between each other. The same principle is exhibited in the jaws of the Porpoise, which are seen on the left of the illustration. The jaws of an Alligator or Crocodile would have answered the purpose quite as well, inasmuch as their teeth interlock in a similar fashion, but I thought that it would be better to give as examples the jaws of allied animals. The reason for this interlocking is evident. All these creatures feed principally on fish, and this mode of constructing the jaws enables them to secure their prey when once seized.
Another example of such teeth is to be found in the fore-legs of various species of Phasma and Mantis, as may be seen by reference to the illustration. The latter insects are wonderfully fierce and pugnacious, fighting with each other on the least provocation, and feeding mostly on other insects, which they secure in their deeply-toothed fore-legs. They use these legs with wonderful force and rapidity, and it is said that a pair of these insects fighting remind the observer of a duel with sabres.
The Baited Trap.
Our space being valuable, we are not able to give many examples of Baited Traps, whether in Art or Nature.
The most familiar example of this trap is the common Mouse-trap, the most ordinary form of which is shown at the right hand of the illustration on page 96. In all the varieties of these traps, whether for mice or rats, the prey is induced to enter by means of some tempting food, and then is secured or killed by the action of the trap. Sometimes these traps are made of considerable size for catching large game, and in Africa are employed in the capture of the leopard, in India for taking both tigers and leopards, and in North America for killing bears.
We have already noticed one instance of a bait in the Angler-fish, described in page 92, but in this case the bait serves only for attraction, and the trap, or mouth, is not acted upon by the prey.
There are, however, many examples in the botanical world, where the plant is directly acted upon by the creature which is to be entrapped, such being known by the now familiar term “Carnivorous Plants.” Of these there is a great variety, but under this head I only figure two of them.
The plant on the right hand is the Venus Fly-trap (Dionea muscipula), which is common in the Carolinas. The leaves of this plant are singularly irritable, and when a fly or other insect alights on the open leaf, it seems to touch a sort of spring, and the two sides of the leaf suddenly collapse and hold the insect in their grasp. The strange point about it is, that not only is the insect caught, but is held until it is quite digested, the process being almost exactly the same as if it had been placed in the stomach of some insect-eating animal.
So carnivorous, indeed, is the Dionea, that plants have been fed with chopped meat laid on the leaves, and have thriven wonderfully. Experiments have been tried with other substances, but the Dionea would have nothing to do with them. The natural irritability of the leaves caused them to contract, but they soon opened and rejected the spurious food.
On the left is the Cephalotus. This plant, instead of catching the insect by the folding of the leaf, secures it by means of a sort of trap-door at the upper end. The insect is attracted by the moisture in the cup, and, as soon as it enters, the trap-door shuts upon it, and confines it until it is digested, when the door opens in readiness to admit more prey.
Birdlime.
By a natural transition we pass to those traps which secure their prey by means of adhesive substances.
With us, the material called “birdlime” is usually employed. This is obtained from the bark of the holly, and is of the most singular tenacity. An inexperienced person who touches birdlime is sure to repent it. The horrid stuff clings to the fingers, and the more attempts are made to clear them, the more points of attachment are formed. The novice ought to have dipped his hands in water before he touched the birdlime, and then he might have manipulated it with impunity.
The most familiar mode of using the birdlime is by “pegging” for chaffinches.
In the spring, when the male birds are all in anxious rivalry to find mates, or, having found them, to defend them, the “peggers” go into the fields armed with a pot of birdlime and a stuffed chaffinch set on a peg of wood. At one end of this peg is a sharp iron spike. They also have a “call-bird,” i.e. a chaffinch which has been trained to sing at a given signal.
When the “peggers” hear a chaffinch which is worth taking, they feel as sure of him as if he were in their cage. They take the peg, and stick it into the nearest tree-trunk. Round the decoy they place half-a-dozen twigs which have been smeared with birdlime, and arrange them so that no bird flying at the decoy can avoid touching one of them.
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