"The appearance," Mr. Wallace adds, "was, however, I dare say, worse than reality, as the bats have the skill to bleed without giving pain, and it is quite possible the horse, like a patient under the influence of chloroform, may have known nothing of the matter. The danger is in the attacks being repeated every night till the loss of blood becomes serious. To prevent this, red peppers are usually rubbed [{189}] on the parts wounded and on all likely places; and this will partly check the sanguinivorous appetite of the bats, but not entirely, as in spite of this application the poor animal was again bitten the next night in fresh places." [Footnote 27]
[Footnote 27: "Travels on the Amazon," p. 44.]
Both Mr. Darwin and Mr. Waterton, if we remember rightly, have borne similar testimony in favor of the opinion that the vampire does suck blood. A servant of the former gentleman, when near Coquimbo, in Chili, observed something attached to the withers of one of his horses, which was restless, and on putting his hand upon the place he secured a vampire bat. Mr. Waterton, however, could not induce the vampires to bite him, notwithstanding the now veteran naturalist [Footnote 28] slept many months in an open loft which the vampires frequented; but an Indian boy who slept near him had his toes often "tapped," while fowls were destroyed, and even an unfortunate donkey was much persecuted, looking, as Mr. Waterton says, "like misery steeped in vinegar."
[Footnote 28: Since this article was in type this excellent naturalist and kind-hearted gentleman has passed away from amongst us.]
While at Villa Nova, on the lower Amazons, our naturalist was subjected to another annoyance, in the shape of ticks. The tracts thereabouts "swarmed with carapátos, ugly ticks, belonging to the genus Ixodes, which mount to the tops of the blades of grass, and attach themselves to the clothes of passers-by. They are a great annoyance. It occupied me a full hour to pick them off my flesh after my diurnal ramble."
Mr. Bates's stay at Ega, on the upper Amazons, and his expeditions in search of scarlet-faced monkeys, owl-faced night-apes, marmosets, curl-crested toucans, blind ants, and hundreds of other interesting animals, must have been particularly enjoyable, if we except the presence of an abominable gad-fly, which fixes on the flesh of man as breeding-places for its grub, and causes painful tumors. "Ega was a fine field for a natural history collector," and Mr. Bates ticketed with the name of this town more than 3,000 new species of animals.
It is an old and a true saying that you "can have too much of a good thing." A London alderman would soon grumble had he to dine every day on turtle only. "The great fresh-water turtle of the Amazons grows in the upper river to an immense size, a full-grown one measuring nearly three feet in length by two in breadth, and is a load for the strongest Indian. . . . . The flesh is very tender, palatable, and wholesome; but it is very cloying. Every one ends sooner or later by becoming thoroughly surfeited." Our traveller adds that he became so sick of turtle in the course of two years that he could not bear the smell of it, although at the same time nothing else was to be had, and he was suffering actual hunger. The pools about Ega abound in turtles and alligators, and the Indians capture a great number of the former animals by means of sharp steel-pointed arrows, fitted into a peg which enters the tip of the shaft. This peg is fastened to the arrow-shaft by means of a piece of twine; and when the missile—which the people hurl with astonishing skill—pierces the carapace, the peg drops out and the struck turtle dives to the bottom, the detached shaft floating on the surface serving to guide the sportsman to his game. So clever are the natives in the use of the bow and arrow, that they do not wait till the turtle comes to the surface to breathe, but shoot at the back of the animal as it moves under the water, and hardly ever fail to pierce the submerged shell.
One of the most curious and interesting facts in natural history is the assimilation in many animals of form and color to other objects, animate or inanimate. Thus the caterpillars termed, from their mode of progression, "geometric" bear so close a resemblance to the twigs of the trees or bushes upon which they rest that it is no easy thing to distinguish them at a [{190}] glance; the buff-tip moth, when at rest, looks just like a broken bit of lichen-covered branch, the colored tips of the wings resembling a section of the wood. The beautiful Australian parakeets, known as the Batcherrygar parrots, look so much like the leaves of Eucalpyti, or gum-trees, on which they repose, that, though numbers may be perched upon a branch, they are hardly to be seen so long as they keep quiet. Some South American beetles (of the family Cassidae) closely resemble glittering drops of dew; some kinds of spiders mimic flower-buds, "and station themselves motionless in the axils of leaves and other parts of plants to wait for their victims." Insects belonging to the genera of Mantis, Locusta, and Phasma, often show a wonderful resemblance to leaves or sticks. Examples of "mimetic analogy" may also be found amongst birds; but perhaps the most remarkable cases of imitation are to be found among the butterflies of the valley of the Amazon recently made known to us by Mr. Bates. There is a family of butterflies named Heliconidae, of a slow flight and feeble structure, very numerous in this South American region, notwithstanding that the districts Abound with insectivorous birds. Now, Mr. Bates has observed that where large numbers of this family are found they are always accompanied by species of a totally distinct family which closely resemble them in size, form, color, and markings. So close is the resemblance that Mr. Bates often found it impossible to distinguish members of one family from those of the other when the insects were on the wing; and he observed, moreover, that when a local variety of a species of the Heliconidae occurred, there was found also a butterfly of another family imitating that local variety. There is no difficulty at all in distinguishing the imitators from the imitated, for the latter have all a family likeness, while the former depart from the normal form and likeness of the families to which they respectively belong. What is the meaning of this curious fact? It is this: the Heliconidae, or imitated butterflies, are not persecuted by birds, dragon-flies, lizards, or other insectivorous enemies, while the members of the imitating families are subject to much persecution. The butterflies imitated are said to owe their immunity from persecution to their offensive odor, while no such fortunate character belongs to the imitating insects. But how, we naturally ask, has this change of color and form been effected? Mr. Darwin and Mr. Bates explain it on the principle of natural selection. Let us suppose that a member of the persecuted family gave birth to a variety—and there is a tendency in all animals to produce varieties—exhibiting a very slight resemblance to some species of Heliconidae. This individual, in consequence of this slight resemblance, would have a better chance of living and producing young than those of its relatives which bear no resemblance whatever to the unmolested family. Some of the offspring of this slightly favored variety would very probably show more marked resemblance to the unpersecuted butterflies; and thus the likeness between insects of totally distinct groups would in course of time be, according to the law of inheritance, quite complete. This is the explanation which Mr. Bates gives of this natural phenomenon. The phenomenon itself is an undoubted one; whether it is or is not satisfactorily accounted for, cannot at present be determined; we must wait for further investigation.
We had intended to speak of some of the South American palms, those wondrous and valuable productions of tropical countries, the India-rubber trees, and other vegetable productions of the Amazons, but we must linger no longer with the excellent naturalist from whose volumes we have derived so much pleasure. Mr. Bates has written a book full of interest, with the spirit of a real lover of nature and with the pen of a philosopher.