Aye-Aye, a word of uncertain signification (perhaps only an exclamation), but universally accepted as the designation of the most remarkable and aberrant of all the Malagasy lemurs (see Primates). The aye-aye, Chiromys (or Daubentonia) madagascariensis, is an animal with a superficial resemblance to a long-haired and dusky-coloured cat with unusually large eyes. It has a broad rounded head, short face, large naked eyes, large hands, and long thin fingers with pointed claws, of which the third is remarkable for its extreme slenderness. The foot resembles that of the other lemurs in its large opposable great toe with a flat nail; but all the other toes have pointed compressed claws. Tail long and bushy. General colour dark brown, the outer fur being long and rather loose, with a woolly under-coat. Teats two, inguinal in position. The aye-aye was discovered by Pierre Sonnerat in 1780, the specimen brought to Paris by that traveller being the only one known until 1860. Since then many others have been obtained, and one lived for several years in the gardens of the Zoological Society of London. Like so many lemurs, it is completely nocturnal in its habits, living either alone or in pairs, chiefly in the bamboo forests.
Observations upon captive specimens have led to the conclusion that it feeds principally on juices, especially of the sugar-cane, which it obtains by tearing open the hard woody circumference of the stalk with its strong incisor teeth; but it is said also to devour certain species of wood-boring caterpillars, which it obtains by first cutting down with its teeth upon their burrows, and then picking them out of their retreat with the claw of its attenuated middle finger. It constructs large ball-like nests of dried leaves, lodged in a fork of the branches of a large tree, and with the opening on one side.
Till recently the aye-aye was regarded as representing a family by itself - the Chiromyidae; but the discovery that it resembles the other lemurs of Madagascar in the structure of the inner ear, and thus differs from all other members of the group, has led to the conclusion that it is best classed as a subfamily (Chiromyinae) of the Lemuridae.