ANTENNE, the articulated flexible horns, on the head of insects ; commonly two in number, and very rarely four. These are such a peculiar and prominent feature, that most of the older entomologists have found ed one of the leading characters of the different genera of insects on their situation, structure, and appearance. All insects, however, are not provided with antenn : in the spider, scorpion, and some monoculi, they are entirely wanting. It is to be observed, in general. that perfect insects, with six legs, have two antenwe ; but that those having more, either want them, or have more than two ; such as crabs and lobsters, if these animals are still to be considered as properly belonging to the insect tribe. Whence, the latest entomologists have rather been disposed to reject the antenna as a constant and invariable characteristic. The horns of snails, and other animals of the genus Mollusca, do not strictly come under the description of antennae, from being re tractile, and wanting articulations.
Most larvae want antenna; ; and although present in several, they are of a very different quality from what they appear in the perfect insect ; from this, however, there are some exceptions, in which they are the same in both.
In the mature insect, the antennae are extremely di versified in size, shape, and organization. In the Noto nrcta, or boat-fly, they can with difficulty be discover ed ; and in the or water scorpion, they are so minute, that intelligent naturalists have been induced to deny their existence. Some consist of only two or three. articulations, such as those of the common fly ; others of between two and three hundred, such as those of the lobster. From this diversity in appearance, they are denominated setaceous, serrated, clavate, filiform, pectinated, and the like. In a few insects they arc short, and terminated by a single hair, as the gadfly ; others are beautifully pectinated, as in various phalence, or resembling tufts of feathers, as in rnusquitoes and ti pulx. Such antenna form the most elegant microsco pical objects.
Not only is there a great difference among the anten na of insects in general, but also in those of the same genus, and even of the same species. The queen bee and workers have fourteen articulations, while the males have only thirteen. The structure of those of the male is likewise sometimes found different ; the male mus quito has feathered antenna, those of the female are fi liform and plain. We should also observe, that the an tenna of quite different kinds of insects are known to resemble each other.
The substance of the antenna is not muscular ; there is only one muscle at the root, directing the motion of the whole. The interior is full of the same pulpous matter, filling the head of insects, which disappears on desiccation. Baster, an able investigator of the nature of marine animals, conceived that there were perfora tions of the skin or integument, through which filaments might issue from within ; but later authors, on repeat ing his experiments, which were made on the lobster, are of opinion, that he has been deceived, either from an optical illusion, or from the adhesion of some extra neous substance. The antenna arc close at the ex tremity, at least the best microscopes can discover no aperture. Mr Kirby has recently observed one pecu liarity, that, in a certain bee, the ten last joints, viewed by a powerful magnifier, appear composed of innume rable hexagons, similar to those of which the eyes of the same insects consist.
Different naturalists have attempted to classify anten na. Ludwig collected 47 different kinds ; but Bonsdorf, going greatly farther, has ascertained 160, which he has subdivided into almost an equal number. Here we shall chiefly direct our attention to a more interesting subject, namely, the purposes for which such organs have heen bestowed.
Nothing has been the source of greater speculation, than the use of antenna ; nor is this surprising, consi dering the variety constantly exhibited in their struc ture, occupation, and appearance. Some insects seem to keep them in continual employment ; in others they are preserved in a quiescent state. Those of an ich neumon, shew an incessant, tremulous, vibratory mo tion, anxiously searching into every crevice, while those of the carrion fly scarcely appear endowed with flexi bility. They have successively been considered as the organs of hearing, feeling, smell, and taste ; or of an unknown and indefinite sense. Although we cannot conceive, that nature would have lavished such a vari ety of structure in vain, or bestowed so conspicuous an organ on myriads of her creatures, to be void of use ; we apprehend that entomologists, struck with such a prominent feature, in the favourite objects of their study, have been too prone to ascribe some certain and exclu sive function to the antennae, without considering, that their sole purpose may be to participate in, and aid the operation of others.