348 TEXTBOOK OF ZOOLOGY 



The last main division of the insect body is the abdomen. It is 

 composed of eleven segments. The seven anterior segments are 

 similar in both the male and female. In the male the first abdominal 

 segment is made up of a curved dorsal shield, the tergum, which 

 terminates just above the attachment of the third pair of legs. This 

 piece partially" surrounds the tympanic membrane, or ear, which is 

 a large, crescent-shaped area covered with a semitransparent mem- 

 brane. The ventral part of the first segment, the sternum, is not 

 attached to the tergum, owing to the large size of the attachment 

 of the legs. The pleura are entirelj'- absent. The second to the 

 eighth segments are all quite similar, consisting of a dorsal tergum, 

 which extends laterally to near the ventral part of the body, where 

 it joins the sternum. The pleura, or side pieces, noted in connection 

 with the thorax, have been inseparably fused to the tergum. In 

 the ninth and tenth segments the terga are partially fused together, 

 the union of the two being indicated by the presence of a transverse 

 suture. The sterna of these two segments are entirely fused and 

 much modified, forming a broad, platelike piece. The eleventh 

 segment is represented only by the tergum, which forms the termi- 

 nal, dorsal, shield-shaped piece (Fig. 201). 



The cerci constitute a pair of plates attached to the lateral posterior 

 border of the tenth segment, and extending back, past the end of 

 the eleventh tergum. The podical plates lie directly beneath the cerci 

 and ventral to the eleventh tergum. The anus opens between these 

 plates, and the genital chamber lies directly below them. Attached 

 to the ninth sternum is the subgenital plate which forms the most 

 posterior ventral plate of the body. 



In the female the eighth segment resembles the other segments, 

 except that the sternum is nearly twice as long, and known as the 

 subgenital plate. The ninth, tenth, and eleventh segments are essen- 

 tially like those of the male, the terga of segments nine and ten 

 being partially fused, and tergum eleven forming the terminal, 

 dorsal shield. The plates called cerci and podical plates are similar 

 to those in the male, except that the podical plates are much more 

 prominent. 



The ovipositor consists of three pairs of movable plates. The 

 dorsal pair lies just ventral to the eleventh tergum and each plate 

 is long, lance-shaped, and with a hard, pointed tip. The ventral pair 

 arises just dorsal to the eighth sternum and resembles the dorsal 



