164 THE COCKROACH. 



the thorax. Its tergum, the pronotum, is pro- 

 longed forwards over the neck. 



b. The mesothorax is smaller, and its tergum bears at 



its anterior corners a pair of elytra, or wing- 

 covers. These are folds of skin and cuticle which 

 extend backwards beyond the hinder end of the 

 abdomen, and are movably articulated to the 

 mesothoracic tergum or mesouotum. 



[The elytra are abortive in the female of P. 

 orientalis.] 



c. The metathorax, or hindmost segment of the thorax, 



bears a pair of wings, which are membranous 

 outgrowths of the body-wall, like the elytra, but 

 broader, thinner, and more movable. By means 

 of these the animal is able to fly. When not in 

 use they are folded longitudinally like a fan and 

 covered by the elytra. 



[The female of P. orientalis has no wings.] 

 4. The abdomen, which forms rather more than half the 

 length of the body, is broad from side to side, 

 especially in the female, and is flattened dorso- 

 ventrally. Its cuticular investment is softer than 

 that of the head and thorax. It is composed of 

 ten distinct segments, but the hinder ones are tele- 

 scoped within one another, so that the full number 

 are not seen at once. The podical plates may 

 represent the tergum of an eleventh segment. 

 a. The terga are cuticular plates covering the dorsal 

 surface of the abdomen and overlapping one 

 another from before backwards. They are broad 

 from side to side, but short from before back- 

 wards. Of the ten only eight are obvious, the 

 eighth and ninth being hidden by the seventh 

 through the telescoping of this part of the body. 

 The tenth is prolonged backwards into a thin hori- 

 zontal plate, deeply notched in its posterior border. 

 [In P. orientalis the eighth and ninth terga 

 are hidden by the seventh in the female only.] 



