ANATOMY AND PHYSIOLOGY 



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to the size and power of the mouth parts. In some insects 

 almost the entire surface of the head is occupied by the eyes, 

 as in Odonata (Fig. 20, B) and Diptera (Fig. 39). In mus- 

 cid and many other dipterous larvae, or " maggots," the head 

 is reduced to the merest rudiment. 



Though commonly more or less globose or ovate, the head 

 presents innumerable forms; it often bears unarticulated out- 

 growths of various kinds, some of which are plainly adaptive, 

 while others are apparently purposeless and often fantastic. 



Sclerites and Regions of the Skull. The dorsal part of 

 the skull (Fig. 33) consists almost entirely of the epicranium, 



FIG. 33- 



B 



Skull of a grasshopper, Melanoplus differentialis. a, antenna; c, clypqus; e, com- 

 pound eye; f, front; g, gena; /, labrum; Ip, labial palpus; m, mandible; mp, maxillary 

 palpus; o, ocelli; oc, occiput; pg, post-gena; v, vertex. 



which bears the compound eyes; it is usually a single piece, 

 or sclerite, though in some of the simpler insects it is divided 

 by a Y-shaped suture. The middle of the face, where the 

 median ocellus often occurs, is termed the front; ordinarily 

 this is simply a region, though a frontal sclerite exists in 

 some insects. Just above the front, and forming the sum- 



