Class Insect a 521 



is a cessation of growth and in adults a stopping of sexual activity. 

 The causative factors of this diapause are not at all clear, but in most 

 cases, it is heat, dryness, or cold. The diapause varies in its duration 

 and usually ceases when favorable conditions return. Possibly it is 

 under the control of endocrine factors which are not at all clearly 

 understood. 



THE ANATOMY OF THE GRASSHOPPER 



In order to understand more details of the anatomy and physiology 

 of insects, the grasshopper has been selected as a type of generalized 

 insect. The grasshopper belongs to the order Orthoptera or straight- 

 winged forms which have an incomplete metamorphosis. A great many 

 species of grasshoppers occur throughout the world. Many are of con- 



Fig. 172. — Front view of head and anterior view of mouth parts of the 

 grasshopper, Romalea sp. 



