THE MANDIBLES 59 



be far more sensitive to movements of the air, to odors, wave-sounds, 

 and light-waves, than any of the vertebrate animals. 



That ants appear to communicate with each other, apparently 

 talking with their antennae, shows the highly sensitive nature of 

 these appendages. " The honey-bee when constructing its cells as- 

 certains their proper direction and size by means of the extremities 

 of these organs." (Newport.) 



How dependent insects are upon their antennae 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 antennae, it falls helpless and par- 

 tially 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 coordi- 

 nating 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 antennae afford salient secondary sexual differences, as seen 

 in the broadly pectinated antennae 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 maxillae. 



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 prin- 

 cipal 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 (Cetoniae) 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 larvse of water-beetles, ant-lions, 

 Chrysopa, etc. where they are perforated at the tips, through which 

 the blood of their prey is sucked. 



While the mandibles are generally regarded as composed of a 



