17 



Epicranial suture. — Observe the inverted Y-shapec sut- 

 ure, the stem of which is on the middle line between the 

 compound eyes, and the arms of which extend towards the 

 antennae ; this is the epicranial suture. 



The stem of the epicranial suture divides the vertex into 

 two sclerites. The arms of this suture separate the vertex 

 from the front, which in this case is not a part of the epi- 

 cranium as it is in the locust. 



Antennal sclerites. — Surrounding the base of each an- 

 tenna there is a more or less distinct, ring-like sclerite ; this 

 is the aniennal sclerite. 



The antennal sclerites are much more distinct in the Plecoptera (stone- 

 flies). 



Clypeo-frontal suture. — The suture separating the cly- 

 peus and the front is obsolete in the cockroaches. Study 

 this suture in the locust, and note the relation of it to the 

 point of articulation of the mandible with the clypeus on 

 each side ; and then indicate the probable position of it in 

 the cockroach by a faint, dotted line in your drawing. 



Letter the vertex, front, clypeus, labrum, and genae. 



Make a preparation showing the lateral aspect of the head 

 and neck, and note the following features : — 



The suture separating the gena from the postgena. 



The absence of a suture separating the occiput from the 

 postgena. 



An opening into the head between the postgena and the neck 

 near the point of attachment of the maxilla. This is the 

 mouth of an invagination of the body-wall which forms a part 

 of the tentorium ; i.e., one of the posterior arms of the tentoriwn. 



A narrow sclerite bounding the mouth of this invagination 

 on the side towards the neck ; this is one of the lateral sclerites 

 of the 77iaxillary segment, the caudal one. 



The maxillary segment is one of several segments that enter into the com- 

 position of the head, and the one of which the maxillae are the appendages, 



