ARTHROPODA. 



259 



5. The abdomen, its degree of development, its seg- 

 ments, and its appendages. 



6. The eyes, simple and compound. 



7. Their haunts and special place of living. 



8. Methods and efficiency of locomotion. 



9. Material used for food in both larval and adult 

 stage and the mode of getting it. 



10. The organs of respiration and their location. 



1 1 . The special senses. 



12. The laying of eggs and provision for the young. 



13. The degree to which they make homes, and the 

 manner of their construction. 



14. The life history. 



15. The difference between the sexes. 



1 6. The degree to which they associate in social life. 



17. Means of defense against enemies. 



1 8. The most conspicuous devices either of structure 

 or instinct that would help to adapt the animal to the 

 conditions of its life. 



[If the available time is short, this exercise may be divided among 

 the members of the class.] 



270. Organs of Special Sense Among the Arthropods. 



Because of the cuticle that covers the body in arthropods, 

 the sensitiveness of the skin cannot be so great as in naked 

 forms. To compensate for this there are numerous special 

 hairs of the same material as the cuticle, which are supplied 

 with nerves from below in such a way as to connect the 

 sensory parts of the organism with the outside conditions. 

 These hairs are usually more abundant on the movable 

 parts, especially those about the head. They may be 

 organs of touch, and, in the case of the male mosquito 

 (Fig. 104), they are believed to be hearing organs. There 

 are several different kinds of organs among arthropods 



