PLATE I. 



Fig. 1. — Head of Cricket. 



This drawing shows the epicranial suture (E. SU.) which divides the 

 paired sclerites from the single ones. 



F. — The front, the first of these single sclerites, between the arms of 

 the inverted Y of the suture, bears here the median ocellus and also the 

 paired ocelli. 



C. — The clypeus. The suture between the front and the clypeus is 

 distinct. The clypeus is partly divided by a transverse suture; the part 

 next the front is designated as first clypeus (ci), and that next the 

 labrum as second clypeus (c2). 



L. — The labrum is the last of the three single sclerites between the 

 arms of the epicranial suture and the mouth. It is a single movable 

 flap, constituting the upper lip of the mouth, having the appearance of an 

 appendage, but in reality is a single sclerite, a portion of one of the head 

 segments. 



Tr. — The trochantin of the mandible is a small sclerite at the base of 

 the mandible (M). 



Fig. 2. — Head of Cockroach. 



E. SU. — The epicranial suture is here present. 



F. — The front bears the paired ocelli, but the median ocellus is absent. 



C. — The clypeus. There is no suture between the front and the cly- 

 peus, but the tentorium, invaginations (at) are quite distinct, and the 

 dotted line connecting these points indicates the position of this obsolete 

 suture. There is no distinct transverse suture dividing the clypeus, but 

 the shading (indicated by second dotted line) gives the appearance of two 

 parts. 



L. — The labrum is present. 



Tr. — The trochantin of the mandible is present. 



Fig. 3. — Head of the Larva of Corj/dalis. 



E. SU. — The epicranial suture here is very low down toward the 

 mouth. 



F. — The fro7it is greatly reduced in comparison with the two forms 

 already studied. The median and paired ocelli are wanting. 



C. — The clypeus. Suture between front and clypeus is absent. Cly- 

 peus divided into three sclerites in transverse row, one on median line 

 called clypeus proper, lateral sclerites called antecoxal pieces of man- 

 dibles (ac). Clypeus proper is divided by definite transverse suture into 

 first and second clypeus {cl and c2). 



Trochantin of mandible not visible. 



At. — Tentorium invaginations present. 



L. — Labrum present. 



O. O. — The occiput as a definite area, formed of the upper portion of 

 the postgenae, is here shown back of vertex (y). 



