How dependent insects are upon their antennæ is seen when we cut them off. The insect is at once seriously affected, its central nervous system receiving a great shock, while it gives no such sign of distress and loss of mental power when we remove the palpi or legs. On depriving a bee of its antennæ, it falls helpless and partially paralyzed to the earth, is unable at first to walk, but on partly recovering the use of its limbs, it still has lost the power of coördinating its movements, nor can it sting; in a few minutes, however, it becomes able to feebly walk a few steps, but it remains over an hour nearly motionless. Other insects after similar treatment are not so deeply affected, though bees, wasps, ants, moths, certain beetles, and dragon-flies are at first more or less stunned and confused. The antennæ afford salient secondary sexual differences, as seen in the broadly pectinated antennæ of male bombycine moths, certain saw-flies (Lophyrus), and many other insects. The mouth-parts, buccal appendages, or trophi, comprise, besides the labrum, the mandibles and maxillæ. =The mandibles.=—These are true jaws, adapted for cutting, tearing, or crushing the food, or for defence, while in the bees they are used as tools for modelling in wax, and in Cetonia, etc., as a brush for collecting pollen. They are usually opposed to each other at the tips, but in many carnivorous forms their tips cross each other like shears. They are situated below the clypeus on each side, and are hinged to the head by a true ginglymus articulation, consisting of two condyles or tubercles to which muscles are attached, the principal ones being the flexor and great extensor (Fig. 48). They are solid, chitinous, of varied shapes, and in the form of the teeth those of the same pair differ somewhat from each other (Fig. 46 _A_). In the pollen-eating beetles (Cetoniæ) and in the dung-beetles (Aphodius, etc.) the edge is soft and flexible. In the males of Lucanus, etc. (Fig. 47), and of Corydalus (Fig. 29), they are of colossal size, and are large and sabre-shaped in the larvæ of water-beetles, ant-lions, Chrysopa, etc. where they are perforated at the tips, through which the blood of their prey is sucked.