FROGS
At the foot of the second of the waterfalls just mentioned I was fortunate enough to see a rather rare frog, which is peculiar to Madagascar. This little creature is only an inch long, as regards the body, but on that and its long hind legs there are semicircular patches of bright red on a black ground, so that it is very conspicuous (Mantella baroni) (see illustration). There is also a much larger frog, three inches in length, with hind legs quite six inches long (Rhacophoras albilabris); this species appears to be, in part at least, arboreal as well as aquatic, as its toes are furnished with little disks instead of claws (see illustration). He is, however, a giant compared with the majority of the frogs found in the island, which are not very different in colouring or size from the common English species. These creatures are very plentiful in the rice-fields, and as one walks along the vàlamparìa, or little banks separating the fields, the frogs jump off and “plop” into the water at every step one takes. In the early morning, after a rainy night, the noise of their croaking is very loud, almost deafening, as they apparently find the increased depth of water much to their liking.
From some small structural peculiarities, many of the Madagascar frogs have been arranged in a distinct genus, called Mantidactylus, and of this genus at least sixteen species have been described. Of the widely distributed genus Rana, one species, R. fasciata, is said by a careful observer to build a kind of nest. These frogs construct regular passages under the grass during the dry season; their paths are made as regularly as those of a mole, by the little creatures pressing down the short grass near the earth, and drawing together the longer blades, thus rendering them invisible. The nests are from eight to ten inches in diameter by four in height, and made ingeniously by weaving the layers of grass together. When frightened, these frogs throw out a limpid stream of water, which has been stored up in time of need, as in very dry weather, and which is distributed over the body, so as to keep the whole of it moist. The tree-frogs are very pretty little creatures, their light green colour exactly matching that of the leaves on which they live, so that it is difficult to detect their presence, except by close inspection. Their toes end in small disks, so as to adhere closely to the smooth surface of the leaves.
We have already seen that many of the living creatures of Madagascar gain great protection from enemies from the assimilation of their colour to that of their surroundings. This is the case also with many species of grasshopper and of mantis. You see an insect with bright scarlet wings flit by you and settle on a bush; wanting to observe it more closely, you try to find it, but it has disappeared, and not a vestige of bright colour is to be seen. Still, if you are patient and search carefully, you may presently see a mantis moving its head about in an uncanny fashion, and its fore legs held up in a mock devotional attitude, from which its specific name of Religiosa has been given it. But the scarlet wings are folded under its green wing-cases so as to be perfectly unseen, and these coverings are just like a leaf, the rest of its body being exactly the colour of its resting-place. In some of the grasshoppers, this mimicry of vegetable forms is still more wonderful. Here is one which resembles green grass, and its body, legs, wing-sheaths and antennæ are all as like grass as they can possibly be. But here again is another kind, whose body is equally imitative of dry grass, and so all parts of it are just like the stalks or the blades of yellowish-brown grass, dried up during the cold season. Even the eyes are imitative, and exactly resemble a small brown seed, such as many grasses bear.
BEETLES
There are many species of beetles to be seen, although none of them are very handsome or conspicuous. The most common kind is a broad flat insect, about an inch long and dull dark brown in colour, which crosses one’s path at every step. Another is seen chiefly on the bushes, a smaller insect, but bright shining jet-black. Another, which appears as if it mimicked a wasp in its habit of flight, is shot with brown and green, with very long legs, and is constantly taking short flights or running rapidly. Another one, but much more rare, has golden-green and metallic tints on its wing-cases. But the insect which has puzzled us most is one that I have seen on a large bush of Ròimémy, a plant with acacia-like leaves, with prickles along the leaf-stalks. This beetle is about five-eighths of an inch long, and almost hemispherical in shape. It is warm reddish-brown in colour, with a line of black and then of yellow next the head, and is perfectly flat below. These insects cluster closely, as thick as they can lie, in groups of from a dozen to more than a hundred together, all round the thicker stems, so that they look at a little distance like strings of large brown beads; and in some of the topmost branches they form a continuous mass for two or three feet. Amongst these shining brown insects are a few others of quite a different colour and shape, perfectly flat, like a minute tortoise, and of a uniform grey, exactly resembling the lichen on the bark of the tree, and the edges of the carapace scalloped. These grey insects are in the proportion of about one to forty or fifty of the darker coloured ones. There are also a few individuals of the same shape as the brown one, but yellowish-green in colour. What these grey insects can be, and what relation they bear to the much more numerous brown ones, I cannot make out.
Other insects, at first sight resembling beetles, are gaudily coloured. Yonder is a bush which is conspicuous from some little distance, from the quantity of insects clustered on it; they are about half-an-inch long, but are most brilliant with scarlet, blue and green. Be careful, however, how you handle them, for their scent is anything but agreeable; and, notwithstanding their gay colours, they are, after all, a species of bug. A beetle which I have often noticed in the woods is an insect an inch and a half long, but with a very long slender proboscis, with which it appears to pierce the bark of the stems on which it rests; I think it feeds on the juices of the bush or tree, and is probably a species of weevil (Eupholus sp?).
MIMICRY
Mimicry, however, is not confined to Madagascar animals, but also occurs among plants. Mr Baron says: “In some marshy ground on the top of Ankàratra mountain, I found a small whitish orchid, a few specimens of which I gathered. After getting about half-a-dozen, I discovered, to my great surprise, that some of them were labiate plants. I was utterly deceived, thinking it was the same plant I was gathering all the time, so exactly alike were the two species in almost all outward appearances. I felt at once convinced that this was a case of mimicry. At the east foot of the mountain I discovered a similar phenomenon, in a large labiate plant (Salvia), strikingly similar to another orchid. No doubt the labiate in each case mimics the orchid, not vice versa, in order to ensure fertilisation.”
In one of our rambles near the large patch of old forest which still remains near the L.M.S. sanatorium at Ambàtovòry I came one day across a cluster of very large earthworms; at first sight these looked more like a number of small snakes than worms, as they were at least three times the size of any English worms, having about as large a diameter as a good-sized man’s finger. They are not, however, very common, as I have only seen them on that one occasion; so they probably do not play the same important part in the renewal of the soil here as Mr Darwin has shown is done by earthworms in Europe.