™ 13 — 



Postgenae.-— On each side veutrad of the occiput and 

 caudad of the gena is a large sclerite. These form the chief 

 portion of the caudal aspect of the fixed parts of the head 

 and may be termed the postgcna. 



The- postgenae and occiput form the boundary of the large 

 opening which connects the cavity of the head with that of 

 the thorax. The postgenae are separated from the epicra- 

 nium by the narrow ridge described above. 



Tentorium — Carefully remove the appendages of the 

 ventral part of the caudal aspect of the head. This may be 

 done by lightly scraping with a knife. It will be seen that 

 the postgenae are connected by a strong part extending 

 from side to side, within the head. This is the tentorium. 



Make a drawing of the caudal aspect of the head just pre- 

 pared ; and name the parts. 



Gula. — When all the parts of the skeleton of the head are 

 present there exists a single sclerite which forms, typically, 

 the ventral part of the cranial box ; this is the gula. In 

 locusts the gula is not well developed, being represented by 

 merely a membrane to which the lower lip is attached. 



Review. — -The fixed parts of the head of a locust consist 

 of five sclerites ; three of these, the occiput and the two post- 

 gence pertain to the caudal aspect, one, the epicranium , con- 

 stitutes the greater part of the dorsal, lateral, and cephalic 

 aspects, and one, the clypeus, forms the ventral portion of 

 the cephalic aspect. The epicranium consists of the vertex, 

 t\\e front and Vaegencz. The gula is not chitinized. 



It should be observed that the head of a locust is bent 

 ventrad so that the mouth is not in the typical position for 

 the mouth of an insect, i. e., at the cephalic end of the head. 

 Imagine the head to be straightened so that the mouth is 

 at the cephalic end of the longitudinal axis of the body and 

 state upon what aspect of the head the clypeus is situated in 

 this case. 



