B18) ENTOMOLOGY 
mit of the head, is the region known as the vertex; it 
often bears ocell. The clypeus is easily recognized as being 
the sclerite to which the upper lip, or labrum, is hinged, 
though the clypeus is not invariably delimited as a distinct 
sclerite. The cheeks of an insect are known as the gene, 
and post-gen@ sometimes occur. On the under side of the 
head is the gula, which bears the under hp, or dabium. That 
part of the skull nearest the prothorax is termed the occi- 
put; usually it 1s not delimited from the epicranium, though 
in some insects it is continuous with the post-genze to 
form a distinct sclerite. The occiput surrounds the opening 
known as the occipital foramen, through which the cesophagus 
and other organs pass into 
the thorax. ‘The membrane 
of the neck in Orthoptera 
and some other insects con- 
BiG. 34: 
tains small cervical sclerites, 
dorsal, lateral or ventral in 
position; these, in the opin- 
ion of Comstock, pertain 
to the last segment of the 
head. Besides those de- 
scribed, a few other cephalic 
sclerites may occur, small 
Blgiliwt = grasshopper, Discsterra. coro. all Cs IICONSpICHOUS, oleae 
pia 2, occipital “fotanien y 42, 4" @mteriov’, “erineless, wot sconclderaisre 
arms of tentorium. 
morphological importance. 
Tentorium.—In the head is a chitinous supporting struc- 
ture known as the fentorium. This consists of a central plate 
from which diverge two pairs of arms extending to the skull 
(Fig. 34). The central plate lies between the brain and the 
subcesophageal ganglion and under the cesophagus, which 
passes between the anterior pair of arms. The tentorium 
braces the skull, affords muscular attachments and holds the 
cephalic ganglia and the cesophagus in place. It is not a true 
internal skeleton, but arises from the same ectodermal layer 
