SCHISTOCERCA AMERICANA DRURY 149 



three joints. At the end of the tarsus are two curved claws and 

 between them a movable lobe, the pulvillus. 



Abdomen. Generally speaking, the skeleton of an ab- 

 dominal somite represents a ring composed of two semicircular 

 sclerites connected with each other and with the preceding and 

 following somites by a thin cuticle. The hind edge of each ring 

 overlaps the anterior edge of the following ring. In the case of 

 the first abdominal somite, however, the tergite and the sternite 

 are disjointed. The tergite terminates above the third leg and 

 bears the chordotonal, auditory organs. The sternite has an 

 anterior process which fits into a corresponding incision of the 

 metasternum and forms a rigid juncture. The ninth and tenth 

 tergites of the male are partially fused and are together only as 

 wide as the ninth sternite. The latter has a terminal plate 

 attached to it known under the name of subgenital plate. At- 

 tached to the posterior edge of the tenth tergite are two movable 

 plates, the cerci. Beneath the latter are two podical plates which 

 belong to the eleventh somite. The sternites of the tenth and 

 eleventh somites are wanting. In the female the ninth sternite 

 is also wanting. The last or eighth sternite has a long median 

 posterior process. The tenth tergite has also cerci as in the male, 

 but they are considerably smaller, while the triangular podical 

 plates of the eleventh somite are much larger. At the end of the 

 abdomen is an ovipositor composed of three pairs of movable 

 parts representing modified appendages. The median pair is 

 called the egg- guides and is much smaller than and partly con- 

 cealed by the other two pairs. 



Integument. The integument consists of a single layer 

 of epithelial cells or hypodermis which secretes a thin supporting 

 membrane to the inside and a more or less thick cuticle to the 

 outside. The cuticle which is nothing else but the exoskeleton 

 is elastic only where it is very thin, /'. e., between the joints, 

 whereas the sclerites or thickened portions of the cuticle are more 

 or less rigid. The animal increases in size with each moulting, 

 while the new cuticle is not yet hardened. The increase in size 



