10 



Make a drawing showing the honey-comb-like structure of 

 the cornea of a compound eye. 



Note. — The drawings illustrating this course should be made with great 

 care, on good paper. Outline drawings are better than those that are shaded, 

 as shading tends to obscure lines indicating sutures. The drawings should 

 be made first with a pencil, then, after they have been criticized, the lines 

 should be inked. 



Simple eyes. — Cephalad of tlie dorsal half of each com- 

 pound eye there is a small transparent hemispherical body. 

 These are the simple eyes. There is a third simple eye situ- 

 ated in a depression near the center of the cephalic aspect of 

 the head. The simple eyes are termed (?f^/// (singular oeelliis). 



Epicranium. — The larger part of the skull appears to 

 consist of a single sclerite which surrounds the compound 

 eyes, and in the locust, bears the simple eyes. This part is 

 termed the epicranium. The cephalic and lateral parts of the 

 epicranium are separated on each side by a suture which ex- 

 tends ventrad from the eye. The ventral ends of these 

 sutures are joined by a very prominent suture which forms 

 the ventral boundary of the cephalic portion of the epicra- 

 nium. 



The epicranium is a compound sclerite, and differs in its 

 extent in different insects. 



Remove the head from the thorax and mount it on a slen- 

 der pin, inserting the pin in the center of the cephalic aspect 

 of the head. The pin will now serve as a handle. 



Note the slightly elevated narrow ridge which separates 

 the lateral from the caudal aspect of the head. This ridge 

 marks the position of the suture which constitutes the caudal 

 border of the epicranium. Upon the dorsal aspect of the 

 head this suture is obsolete. 



Upon each side joining the ventral end of the suture just 

 described and the ventral end of the one which extends ven- 

 trad from the compound eye is a well-marked suture, which 



