272 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 1 37 



same time the imaginal fat body is reduced in size (fig. 6). During 

 the next ^^2 hours, the cells of the larval fat body diminish steadily 

 in size and in fat and protein content, while the adult fat body is con- 

 comitantly enlarging with the deposition of large amounts of glycogen, 

 especially, to a maximum on this third day, at the end of which the 

 larval fat body cells have disappeared. This mature histological picture 

 of the fat body does not change for 4 to 5 weeks after emergence. 

 Thus, these two reports supply firm histological, biochemical, and 

 functional evidence for maturation of flight ability within a few days 

 after the appearance of the adult fly. 



Table 2. — Changes in the glycogen concentration in Drosophila funebris as a 

 junction of adult age 



(After Williams et al., 1943.) 



CYTOCHROME OXIDASE ACTIVITY IN THE YOUNG IMAGO 



Early studies of the physiology of metamorphosis were concerned 

 with the typical, U-shaped curve for oxygen consumption during the 

 pupal stage of holometabolous insects ; but this index of metabolism 

 was not followed into the adult stage. With the recent increased in- 

 terest in insect biochemistry, the cytochrome system has been studied 

 by Sacktor (1951) in the house fly. (The components of this system 

 mediate electronic transfer from metabolic intermediates ultimately 

 to oxygen and therefore effect the final steps of aerobic oxidation. 

 As such, a knowledge of the details of their changes during metamor- 

 phosis would pinpoint the controlling basic respiratory processes in- 

 volved.) He found that cytochrome c oxidase activity followed a 

 typical U-shaped curve during pupal development (for both normal 

 and DDT-resistant strains). Furthermore, in following this activity 

 into adult life (1950), he found that the enzyme activity continued its 



