STRUCTURES USED IN CLASSIFICATION. 



21 



IZU.- 



pad or pulviUus (p) which, by its adhesion to foreign bodies, 

 serves as a point of resistance in leaping. The second joint is 

 much shorter and carries a smaller pad. The third joint is long 

 and slender, with two curved pointed claws or ungues (un), be- 

 tween which is a concave sucking disk or pad, known as the 

 aroUum. 



THE ABDOMEN. The abdomen or hind portion of the body of 

 the locust (Fig. 1) is composed of ten more or less complete seg- 

 ments, so united as to be movable in a small degree. Each seg- 

 ment is composed of two parts, a tergum or upper portion, and a 

 sternum or under piece. The tergum is crested or bent in the 

 median line to form a ridge, the two sides, sloping downward, be- 

 ing known as tcrgitcs. The sternum of the first or basal ab- 

 dominal segment is united firmly to that of the metathorax. The 

 tergites of this segment, in the locust, each contain a large open- 

 ing closed by a membrane, the auditory organ or ear. However, 



the ears of many Orthoptera are 

 borne upon the basal portion of 

 the front tibiae. Eight of the 

 abdominal segments of the lo- 

 cust have a small opening on the 

 lower margin of each tergite. 

 These are spiracles or external 

 openings of tubes which serve as 

 air passages. The ninth and 

 tenth abdominal segments of the locust are more or less modified 

 in both sexes. The abdomen of the female ends in a double pair 

 of short curved movable horny plates, known as the valves of the 

 ovipositor. In the other families of Orthoptera in which the ovi- 

 positor is visible, these plates vary greatly in form and size. The 

 valves in the female locust are used in forcing the earth aside, 

 thus forming a pit in which the eggs are deposited. Between and 

 hidden by them is the ovipositor proper. 



The ventral portion of the last abdominal segment of the male 

 locust is a large, upcurved, spoon-shaped piece known as the suit- 

 genital plate. Attached to the tergum of the next to the last seg- 

 ment are a pair of appendages known as the cerci. In the male 

 locust these are unjointed, and in the different species vary much 

 in size and shape, often affording valuable characters for classifi- 

 cation. In many of the other families they are jointed, and more or 



Auditory organs 

 locust; (B) of a 

 (.After Lugger.) 



or ears 

 katydid. 



