ANTENNA

(Lat. a yard arm.) A moveable, tubular, and jointed sensiferous organ situated on the head; and peculiar to the Condylope Articulata. Certain Ann elides carry soft tentacles or filaments upon the head, which have been termed antennae; but improperly, according to the above definition, which would restrict the phrase to the jointed antennae of insects and crustaceans. In the latter cla the antennae are commonly four in number, consisting each of a ' scape,' a ' pedicel,' of two joints, and a ' clavolet '; the latter is setaceous, and divided into a vast number of minute joints. It is simple in the external antennae, but in the internal pair is always composed of two and sometimes of three setaceous filaments. The internal pair of antennae are situated before or between the eyes, the external behind, at the outer sides of the eyes. In insects the antennae are always two in number, and situated in the space between or before the eyes; they consequently correspond to the internal antennae of crustaceans. The cavity or socket in which the base of the antennae is planted is called the ' torulus,' or bed. The first, and in many cases the most conspicuous, joint of the antennae is termed the scape. The base of the scape, by which it is articulated with the toirulus, is the bulb. -It often looks like a distinct joint, and is the point upon which the antenna tuins. The ped i cell us, or second joint of the antenna, in some insects, also acts the part of a pivot in the bed of the scape, in order to give a separate motion to the clavola, or clavolet. This, which includes the remaining joints of the antenna taken together, is occasionally terminated by a capitulum or knob; a term applied to the last joints of the clavolet when suddenly larger than the rest. (For the varieties of antennae with respect to situation, approximation, proportion, direction, figure, termination, and appendages, the reader is referred to the 4th vol. of Kirby and Spence's Introduction to Entomology.) ANTENNUL^. (Dim. of antenna.) A term sometimes applied to the articulated filaments attached to the jaws or lower Up of Mandibulate insects, and which seem to be endowed with a sensiferous faculty specially adapted to distinguish kinds of food, and applied by the animal to that use: these organs are more commonly called palps, palpi, or feelers. [s. 71]