THE APPENDAGES OF THE HEAD. 



27 



organs ; while the same iirsect, when evidently affected by 

 sounds, keeps them motionless in one direction, as if in the act 

 of listening." (Newport.) 



After cutting off one or both antennae of the June beetle, 

 Lachnosterna, the insect loses its power of directing its flight 

 or steps, wheeling about in a senseless manner. Dr. Clemens 

 observed that the Cecropia moth was similarly affected after 

 losing its antennae. 



The Mandibles (Fig. 37) are inserted on each side of the 

 mouth-opening. They usually consist of but a single joint, 



Fig. 37. 



representing probably the basal part of the ideal limb. This 

 part, however, is often subdivided by two longitudinal furrows 

 into three parts, each ending in a "tooth" of unequal size for 

 tearing and cutting the food. This tripartite form of the man- 

 dibles, to which attention has been called by Mr. Scudder, is 

 more fully carried out in the maxilla, where each portion is 

 highly specialized. The mandibles vary greatly in form and 

 size. The two cutting edges are usually opposed to each other, 

 or frequently overlap in the carnivorous forms. Their base is 

 often concealed by the clypeus 

 and labrum. Their motion is 

 transverse, being the reverse of 

 the motion of the jaws of Ver- 

 tebrates. 



Fig. 38. b The JfoazKce(Figs.38&,39)are Fig. 39. 



much more complicated organs than the mandibles. They are 



FIG. 37. Different forms of mandibles. A, mandible of Cicindelapurpurea; B, 

 Phylloptera, a green grasshopper; C, Libellula trimaculata; D, Vespa maculata, or 

 paper-making Wasp ; E, " rostrum" or jointed sucker of the Bed-bug, Cimex lectu- 

 larius, consisting of mandibles, maxillae, and labium; F, proboscis, or sucker, of a 

 Mosquito, Culex, in which the mandibles are long and bristle-like. From Sanborn. 

 G, mandible of Amphizoa ; H, mandible of Acratus, a genus of Cockchafers. From 

 Horn. 



FIG. 38. a, mentum and labial palpi; b, one maxilla, with its palpus, of Acra- 

 tus. From Horn. 



FIG. 39. Maxilla of Amphizoa, with the two lobes (stipes and lacinia), and the 

 palpifer bearing the four-jointed palpus. From Horn. 



