Page:Jardine Naturalist's library Entomology.djvu/110

104 figure and proportion of the joints are very variable; the terminal joint especially exhibits a great variety of forms, which are of great service in distinguishing genera. The number of joints never exceeds six. Closing the mouth on the underside is a piece which acts as an antagonist to the upper lip, and has therefore been named the under lip or labium. The basal portion of this constitutes the mentum or chin; which is a quadrangular, trapezoidal or semi-circular plate. The part immediately adjoining this and anterior to it, is the labium properly so called, usually bearing the labial palpi. The terminal portion is the ligula or limb, frequently divided into lobes. The labial palpi are similar in structure to the maxillary pair, but they always consist of a smaller number of joints, the greatest amount never exceeding four. The tongue (lingua) is usually a very obscure member of the trophi, and authors do not always assign that name to the same organ. It may be described as the lining membrane of the under lip, the anterior angles of which sometimes protrude in front, as may be seen among the Carabidæ, a tribe in which the projecting points have been named paraglossæ. It is most distinct among the orthoptera. On examining a mouth formed for suction, it appears, at first sight, to be constructed on such a different model from that just described, that it seems almost a hopeless case to attempt to trace any analogy between the parts. But it is not long before we can discover an essential agreement, although the