METACHEMOGENESIS IN INSECTS — ROCKSTEIN 



273 



ascending tendency by increasing by over 50 percent from 30 minutes 

 to 2 hours of age and by 100 to 200 percent by the third day (figs. 7 

 and 8). Bodenstein and Sacktor (1952) found a similar U-shaped 

 curve during pupal development of Drosophila virilis Sturtevant, 

 for cytochrome c oxidase activity, which continued well into the adult 

 stage, with the enzyme activity at emergence equal to that at the 

 beginning" of pupation. After emergence the enzyme continued to 







Fig. 6. — Accumulation of glycogen in fat body and halteres in the young fly. 



A, Imaginal fat body of newly emerged fly. A', larval fat body of the same. 



B, Imaginal fat body at 48 hours. B', Larval fat body of the same. C, Imaginal 

 fat body at 4 days. D, Haltere of newly emerged fly. E, Haltere at 48 hours. 

 F, Haltere at 4 days, showing progressive increase in glycogen, a, Glycogen; 

 b, fat; c, protein spheres. (After Wigglesworth, 1950.) 



increase to a maximum at the end of the third day (see fig. 9), equal 

 to double the activity of the newly emerged imago. It is interesting 

 that Keilin (1925), in his identification of cytochrome in a variety of 

 animals, recognized that its presence in insect flight muscles might 

 be related to their ability to contract at high rates ; more important to 

 this discussion, he found that the cytochrome content of newly- formed 

 adult thoracic flight muscles increases during pupal development, and 



