20 



that there are apparently but two terminal lobes, and these 

 distinct only distally, or all of the terminal lobes may fuse to 

 form a simple flap-like sclerite, as among some of the Neu- 

 roptera. Because of this fusing of the bases or of all of the 

 terminal lobes they are often spoken of collectively as the 

 lignla (see p. 14. in account of external anatomy of the 

 locust). 



Hypopharynx. The hypopharynx is a fleshy, blunt- 

 pointed, tongue-like lobe, supported by a chitinized frame- 

 work ; this chitinous framework at the basal part of the 

 hypopharynx projects backwards as four slender rods, two 

 dorsal and two ventral, the ventral ones being curved and 

 shorter than the upper. This chitinous framework is called 

 the pharyngeal skeleton. 



Make drawings of all the mouth-parts of the cockroach, 

 naming the sclerites. 



Cervical sclerites. Study the neck of the cockroach 

 and note that there are eight cervical sclerites, two dorsal, 

 two ventral and two on each lateral aspect. 



THE PARTS OF THE THORAX. 



Division into segments. Return to the study of the 

 locust. The thorax consists of three segments. The cephalic 

 or first segment is named the prothorax ; the second or inter- 

 mediate, the mesothorax ; and the third or caudal, the met- 

 athorax. 



These divisions of the thorax can be easily recognized by 

 the appendages they bear. To the prothorax is articulated 

 the first pair of legs ; to the mesothorax are joined the sec- 

 ond pair of legs and the first pair of wings ; and to the 

 metathorax, the third pair of legs and the second pair of 

 wings. 



