« AnteriorContinuar »
the wings are so held that all combine to mimic with extraordinary fidelity a dead leaf still attached to the twig by a short pedicle or leaf-stalk imitated by a short tail on the
hind wings, and showing midrib, oblique veins, and, most remarkable of all, two apparent holes, like those made in leaves by insects, but in the butterfly imitated by two small circular spots free from scales and hence clear and transparent. With the head and feelers concealed beneath the wings, it makes the resemblance wonderfully exact.
There are numerous instances of special protective resemblance among spiders. Many spiders (Fig. 220) that
live habitually on tree trunks resemble bits of bark or small, irregular masses of lichen. A whole family of spiders, which live in flower-cups lying in wait for insects, are white and pink and party-colored, resembling the markings of the special flowers frequented by them. This is, of course, a
Fig. 221.-A pipe-fish (Phyllopteryx) resembling sea-weed, in which it lives.
special resemblance not so much for protection as for aggression; the insects coming to visit the flowers are unable
to distinguish the spiders and fall an easy prey to them. br. 283. Warning colors and terrifying appearances.—In the
cases of advantageous coloring and patterning so far dis
cussed the advantage to the animal lies in the resemblance between the animals and their surroundings, in the inconspicuousness and concealment afforded by the coloration. But there is another interesting phase of advantageous coloration in which the advantage derived is in rendering the animals as conspicuous and as readily recognizable as possible. While many animals are very inconspicuously colored, or are manifestly colored so as to resemble their surroundings, generally or specifically, many other animals are very brightly and conspicuously colored and patterned. If we are struck by the numerous cases of imitative coloring among insects, we must be no less impressed by the many cases of bizarre and conspicuous coloration among them.
Many animals, as we well know, possess special and effective weapons of defense, as the poison-fangs of the venomous snakes and the stings of bees and wasps. Other animals, and with these cases most of us are not so well acquainted, possess a means of defense, or rather safety, in being inedible—that is, in possessing some acrid or illtasting substance in the body which renders them unpalatable to predaceous animals. Many caterpillars have been found, by observation in Nature and by experiment, to be distasteful to insectivorous birds. Now, it is obvious that it would be a great advantage to these caterpillars if they could be readily recognized by birds, for a severe stroke by a bird's bill is about as fatal to a caterpillar as being wholly eaten. Its soft, distended body suffers mortal hurt if cut or bitten by the bird's beak. This advantage of being readily recognizable is possessed by many if not all illtasting caterpillars by being brilliantly and conspicuously colored and marked. Such colors and markings are called warning colors. They are intended to inform birds of the fact that the caterpillar displaying them is an ill-tasting insect, a caterpillar to be let alone. The conspicuously black-and-yellow banded larva (Fig. 147, 6) of the common
Monarch butterfly is a good example of the possession of warning colors by distasteful caterpillars.
These warning colors are possessed not only by the illtasting caterpillars, but by many animals which have special means of defense. The wasps and bees, provided with stings—dangerous animals to trouble—are almost all conspicuously marked with yellow and black. The lady-bird beetles (Fig. 222), composing a whole family of small beetles
which are all ill-tasting, are brightly and conspicuously colored and spotted. The Gila monster (Heloderma), the only poisonous lizard, differs from most other lizards in being strikingly patterned with black and brown. Some of the venomous snakes are conspicuously colored, as the coral snakes (Elaps) or coralillos of the tropics. The naturalist Belt, whose observations in Nicaragua have added much to our knowledge of tropical animals, describes as follows an interesting example of warning colors in a species of frog: “In the woods around Santo Domingo (Nicaragua) there are many frogs. Some are green or brown and imitate green or dead leaves, and live among foliage. Others are dull earth-colored, and hide in holes or under logs. All these come out only at night to feed, and they are all preyed upon by snakes and birds. In contrast with these obscurely colored species, another little frog hops about in the daytime, dressed in a bright livery of red and blue. He can not be mistaken for any other, and his flaming breast and blue stockings show that he does not court concealment. He is very abundant in the damp woods, and I was convinced he was uneatable so soon as I made his acquaintance and saw the happy sense of security with which he hopped about. I took a few specimens home with me, and tried my fowls and ducks with them, but none would touch them. At last, by throwing down pieces of meat, for which there was a great competition among them, I managed to entice a young duck into snatching up one of the little frogs. Instead of swallowing it, however, it instantly threw it out of its mouth, and went about jerking its head, as if trying to throw off some unpleasant taste.”
Certain animals which are without special means of defense and are not at all formidable or dangerous are yet so marked or shaped and so behave as to present a threatening or terrifying appearance. The large green caterpillars (Fig. 223) of the Sphinx moths—the tomato-worm is a familiar one of these larvæ—have a formidable-looking,
Fig. 223.-A “tomato-worm” larva of the Sphinx moth, Phlegethontius carolina,
showing terrifying appearance.
sharp horn on the back of the next to last body ring. When disturbed they lift the hinder part of the body, bearing the horn, and move it about threateningly. As a matter of fact, the horn is not at all a weapon of defense, but is quite harmless. Numerous insects when disturbed lift the hind part of the body, and by making threatening mo