ANATOMY AND PHYSIOLOGY 29 
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 larvee, 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, 
Skull of a grasshopper, Melanoplus differentialis. a, antenna; c, clypeus; e, com- 
pound eye; f, front; g, gena; /, labrum; /p, 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 1s 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- 
