The aye-aye is included among the four-handed animals, but it is very unlike the monkeys, having a smaller brain and much less intelligence; and from its powerful teeth it was at first thought to be a link between them and the rodentia, or gnawing animals. Its structure presents some of the most interesting illustrations of typical forms, being modified to serve special ends that any animal organisation can exemplify. The food of the aye-aye consists of a wood-boring larvæ, which tunnels into the wood of certain trees. To obtain these, the animal is furnished with most powerful chisel-shaped incisor teeth, with which it cuts away the outer bark. As, however, the grub retreats to the end of its hole, one of the fingers of the aye-aye’s hands is slightly lengthened, but much diminished in thickness, and is finished with a hook-like claw. Thus provided, the finger is used as a probe, inserted in the tunnel, and the dainty morsel drawn forth from its hiding-place. There are also other modifications, all tending to the more perfect accomplishment of the purposes of its creation: the eyes being very large to see in the night, the ears widely expanded to catch the faint sound of the grub at work, and the thumbs of the feet largely developed so as to enable the animal to take a firm hold of the tree while using its teeth.

Since then, living specimens of the aye-aye have been sent to Europe, and careful observations were made for several months on the habits of one in the Regent’s Park Gardens; and other information has been obtained as to the animal as observed in its native forests by intelligent natives. The creature somewhat resembles a large cat in size, being about three feet in total length, of which its large bushy tail forms quite half. Its colour is dark brown, the throat being yellowish-grey; a somewhat silvery look is given to the fur in certain lights by many whitish hairs on the back. The probe finger is used as a scoop when the aye-aye drinks; it is carried so rapidly from the water to the mouth that the liquid seems to pass in a continual stream. A remarkable fact has been pointed out in the structure of the lower jaw—namely, that the two sides are only joined together by a strong ligament, and do not, as in other animals, form one connected circle of bone. This accounts for the prodigious power of gnawing that the aye-aye possesses. It was seen to cut through a strip of tin-plate nailed to the door of its cage.

The aye-aye constructs true nests, about two and a half feet in diameter, which are found on trees in the dense parts of the forest. Near the coast these are composed of rolled-up leaves of the traveller’s tree, and are lined with twigs and dry leaves. The opening of the nest is at the side, and a small white insect called andaitra, probably the larva of some beetle, forms the animal’s chief food. It is said to be very savage, and strikes rapidly with its hands. The coast people believe it to be an embodiment of their forefathers, and so will not touch it, much less do it an injury; and if they attempted to entrap it, they think they would surely die in consequence; and their superstition extends even to its nest.

The aye-aye is one of the many instances which the animal life of Madagascar presents of isolation from other forms. It remains the only species of its genus, and, like many of the peculiar birds of the island, is one of the many proofs that Madagascar has for long ages been separated from Africa; so that while allied forms have become extinct on the continent, here, protected from the competition of stronger animals, many birds, mammals and insects have been preserved, and so this island is a kind of museum of ancient and elsewhere unknown forms of life.