64 HOW ARE ANIMALS AND PLANTS DEPENDENT? 



covered by two flaps, the upper and lower lips. The leaf upon 

 which the grasshopper feeds is held in place in the mouth by means 

 of the maxillae, while it is cut into small pieces by the mandibles. 

 Eyes. An examination of the compound eye of a grasshopper 

 with a lens shows the whole surface to be composed of tiny six- 

 sided lenses called facets (fas'ets). Each facet marks the surface 



of a unit (ommati- 



dium) of the com- 

 pound eye. Each 

 unit probably gives a 

 separate impression 

 of light and color. 

 Since each unit is 

 separated from its 

 neighbor by a layer 

 of pigment, a com- 

 pound eye is most 

 favorable for per- 

 ceiving the move- 

 ment of ob j ec ts . The 

 grasshopper also has 

 three simple eyes, or 

 ocelli, on the front of 



the head. The simple eyes probably are able only to perceive 



light and darkness. 



Practical Exercise 2. Explain why an insect easily perceives a moving object. 



Other sense organs. The segmented feelers, or antennae, have 

 to do with the sense of touch and smell. The auditory organ or 

 ear of the grasshopper is found under the wing on the first segment 

 of the abdomen. Covering the body and on the appendages are 

 found sensory hairs which make the insect sensitive to touch. 

 Thus the armor-covered animal is put in touch with its 

 surroundings. 



Life history. In the fall of the year the female grasshopper 

 digs a hole in the ground. She thrusts her abdomen into the hole 

 and lays from twenty to thirty eggs in small oval or bean shaped 



Life history of a grasshopper. Explain what is meant by a 

 life cycle ; a metamorphosis. 



