7 6 COMPARATIVE ANATOMY AND PHYSIOLOGY. 



muscles and serve for flight ; or one pair only is 

 developed, or is developed in one sex only, or both 

 pairs are more or less rudimentary. The organs of 

 the mouth are adapted for biting and cutting, or for 

 sucking, and the abdominal metameres are often more 



Fig. 35. Cockroaches : A, Male ; B, Female ; c, Young. 



or less reduced ; the generative pores are placed far 

 back, and respiration is always effected by tracheal 

 tubes or modifications thereof. 



a. Man dib ill at a. In this series the mouth 

 organs are adapted for cutting and biting, and move 

 from side to side ; or are converted into licking 



organs. 



1. Orthoptera : cockroaches, grasshoppers, and 

 locusts. With the anterior pair of wings converted 



