IV. INSECTA: HEXAPODA. 463 



The appendages (fig. 484), seven pairs, are confined to the head 

 and thorax (see, however, infra). The three thoracic segments 

 bear three pairs of legs, whence the name Hexapoda. The legs are 

 inserted between pleura and sterna and begin with a short coxa 

 (c), followed by a trochanter (tr), also short. The two following 

 joints are long, the first, the femur (/<?), being large and contain- 

 ing the muscles; the next, tibia (t), being more slender; the foot, 

 or tarsus (ta), is composed of a series of joints, the last bearing a 

 pair of claws. 



The first of the cephalic appendages, the antennae, are the 

 most leg-like, but normally are never clawed. They spring from 

 the frons above the mouth and are innervated from the brain. 

 The number and shape of the antennal joints varies with the 

 group, and according as the single joints are lengthened or short- 

 ened, narrowed or expanded, or provided with appendages, etc., 

 different kinds of antennae knobbed, club-shaped, toothed, feath- 

 ered, etc.- 2 are recognized, distinctions of great value in classi- 

 fication. 



The morphology of the three pairs of mouth parts, the mandi- 

 bles (md), maxillae (mx), and second maxillae, or labium (la, figs. 

 486-489), is more interesting. The labium, formed of united 

 right and left appendages, lies behind the mouth and forms the 

 lower lip, and is in contrast to the upper lip, or labrum (lr)> 

 which, however, is not appendicular in character. Both labium 

 and labrum may bear unpaired processes on their oral surfaces, an 

 epipharynx above, a hypopharynx below the mouth, neither of 

 them true appendages. 



The different kinds of food necessitate differences in the char- 

 acter of the mouth parts, chewing, licking, sucking, or piercing 

 all referable back to the chewing kind, and these in turn are 

 modified legs. In the description of the chewing type it is well 

 to begin with the maxillae (fig. 486), because of their easy com- 

 parison with the other mouth parts and with the legs as well. 

 These begin with a triangular joint, the cardo (c), which is fol- 

 lowed by a larger stipes (st). The stipes in turn supports two 

 chewing lobes, the inner, or lacinia (li), and an outer, or galea (le), 

 these being processes segmented off from the stipes. In the 

 Orthoptera and Coleoptera only the lacinia is sharp-pointed ; the 

 galea may either form a sheath for the lacinia, or, as in many beetles 

 (fig. 514), it may be tactile and jointed again. The stipes also 

 bears the maxillary palpus (pm), consisting of from three to six 

 similar joints, and is the mostly leg-like part of the appendage. 



