THE GRASSHOPPER 117 



3. Thorax. Distinguish the Following divisions: (a) 

 prothorax, (6) mesothorax, (c ) metathorax. These three parts 

 of the thorax represent somites. Are they sharply separated 

 from each other? Do they move? In what respects do 

 they correspond to typical segments of the crayfish? Ob- 

 serve the several plates of which each is composed. What 

 appendages are borne by each somite? 



4. Appendages of the Thorax. (a) Legs. How many? 

 Distinguish the following joints: coxa, a short segment 

 next to the body; trochanter, the second segment, which 

 may be fused with the first in the jumping legs; femur, 

 the middle segment; tibia; tarsus or foot. Is the tarsus 

 a single piece? Compare the several parts of each of the 

 legs with corresponding portions of the others. In what 

 are they alike ? In what different ? 



(6) Wings. How many? On which somites are they 

 borne? Note their size, color, and texture. What is their 

 relative position in repose? In flight? Spread the wings 

 and study the arrangement of the veins. 



Make drawings of the first and third legs, and of both pairs 

 of wings. 



5. Abdomen. Of how many somites is it composed? 

 Compare the male and female specimens carefully in shape, 

 size, number and relations of the somites. In what partic- 

 ulars do they differ? Compare the first somite with those 

 following and note any differences. In this somite there 

 is a membranous tympanum or ear drum. 



Study the structure of a somite and observe a dorsal 

 portion, the tergum and a ventral sternum. Are these parts 

 well marked? Are they present in each somite? Are the 

 terga and sterna capable of movement? 



In the side walls of the somites are small openings or 

 pores called spiracles. These are the external openings of 



