METACHEMOGENESIS IN INSECTS — ROCKSTEIN 



271 



X 



o 



> 



o 



z 



UJ 



o 



O I 



o 



AGE (days) 



Fig. 4. — Changes in the glycogen concentration of Drosophila as a function of 

 the animals' adult age. (After Williams et al., 1943.) 



u. 

 o 



z 



40 O 



H 

 < 

 K 



=> 

 Q 



ACE (DAYS) 



Fig. 5. — The relation between the flight ability and the age of Drosophila. 

 Upper curve, average duration of flight as a function of age. Lower curve, aver- 

 age total number of wing beats as a function of age. (After Williams et al., 

 1943.) 



