INSECTA 



117 



The wings are borne on the last two segments of the thorax. 

 The first pair are thickened to form a protection to the mem- 

 branous hinder pair, and are called elytra. In the male the 

 elytra reach to the fifth abdominal segment. The posterior 

 pair are thin and membranous, and are the organs of flight on 



Mandibles 



Naxilla 



Stipes 



Cardo 



FIG. 57. Blatta. Mouth parts in detail. 

 NOTE. The lacinia of the labium is often termed the ligula. 



the rare occasions when flight is resorted to by the males. 

 In the female, both the elytra and the wings are rudimentary. 



The segments of the abdomen number ten, and each is 

 resolved into a tergum and a sternum. The anal opening is 

 terminal, and the genital opening is ventral to it. A pair of 

 podical plates situated one on each side of the anus is believed 

 to represent an eleventh segment. In both sexes the first 

 segment is small, but sex produces differences with regard to 

 the posterior segments. In the male the eighth and ninth 

 segments are apparent, but in the female they are telescoped 



