— II — 



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 usually termed ocelli ; some- 

 times, stemmata (singular stem ma). 



When the term ocelli is used in descriptive works, if there 

 is nothing in the context to indicate the contrary, it is al- 

 most invariably applied to the simple eyes, and not to the 

 elements of the compound eyes. In the same way the term 

 eyes usually refers to the compound eyes unless other- 

 wise indicated by the context. 



Epicranium. — The simple eyes are situated in, and the 

 compound eyes surrounded by a large sclerite which consti- 

 tutes the greater portion of the fixed parts of the head or 

 cranial box. This sclerite is the epkranium. The cephalic 

 and lateral parts of the epicranium are separated on each 

 side by a suture which extends ventrad from the eye. The 

 ventral ends of these sutures are joined by a very prominent 

 suture which forms the cephalic boundary of the cephalic 

 portion of the epicranium. 



Remove the head from the thorax and mount it on a 

 slender 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 head this suture is obsolete.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 

 forms the ventral border of the lateral part of the epicran- 

 ium. 



(a.) Vertex. — The dorsal part of the epicranium is called 

 the vertex. 



