34 



ARTHROPODA 



tarsus. Between the two claws at the end of the tarsus 

 is a little pad, the pulvillus, which enables the animal to 

 walk on smooth surfaces. Directly behind the bases of 

 the antennae are the two large compound eyes composed 

 of hundreds of cones whose ends, called facets, may be seen 

 on the surface with a good hand lens or low power of the 

 compound microscope. Three ocelli, or simple eyes, well 

 seen with a hand lens, are also present. As hi most insects, 



the median one is between 



the antennae and the lateral 

 ones just in front of the 

 compound eyes. The ear 

 is a circular opening covered 

 by membrane on the side 

 of the first abdominal seg- 

 ment. On the lateral aspect 

 of each of the eight anterior 

 segments of the abdomen 

 and the two posterior seg- 

 ments of the thorax is a 

 minute opening barely vis- 



Photograph of a spiracle with ible to the naked eye. It 

 is the spiracle, which admits 

 air to a tube branching 

 profusely among the tissues for the purpose of supplying 

 all parts with oxygen and carrying away the carbon 

 dioxide formed in every region of an animal's body. 

 These ramifying tubes, called trachece, are common to all 

 insects and a few other Arthropoda. 



Destruction of Crops. Locusts have always been a 

 great pest to man, as may be inferred from the destructive 



FIG. 10. 



Its tracheae removed from an insect. 

 , spiracle. Three times natural size. 



