280 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 1 37 



has a regulatory influence upon body metabolism in general, possibly 

 by the release of a metabolic hormone which influences the composition 

 of the fat body and oenocytes as well as total body metabolism (as re- 

 flected by oxygen uptake of normal and allatectomized animals of 

 either sex). 



Bodenstein and Sacktor's study (1952) attempted to show hor- 

 monal-enzymatic interrelationships of the (prothoracic gland and) 

 corpus allatum and cytochrome oxidase activity (see fig. 9, above) 

 during the late pupal and early imaginal life of Drosophila virilis. Al- 

 though considerable evidence has been accumulated by a number of 

 endocrinological studies that the corpora allatum is active from the 

 late pupal stage onward in several insect species, there was found no 

 direct relation between rising enzyme activity and the activity of this 

 gland. Thus, allatectomy in animals 3 hours after emergence failed 

 to arrest the usual progress of rapidly rising cytochrome oxidase 

 during the first 3 days of adult life. It is likely that the failure to 

 demonstrate this interrelationship may have arisen from the fact that 

 the corpus allatum actually triggers such enzyme production and re- 

 lease, considerably earlier than the time at which allatectomy was per- 

 formed, especially inasmuch as the rise in the enzyme activity has 

 already begun on the second to third day after the pupal stage (see 

 fig. 9). Although the mediation of the extrinsic control of metamor- 

 phosis itself through the associated cytochrome system has been 

 clearly indicated by the integrated studies of Williams and his co- 

 workers (1951) in the developing pupa of Platysamia cecropia (Lin- 

 neaus), such a relationship has not been studied beyond the immediate 

 end of the pupal stage and the newly emerged adult insect. From the 

 standpoint of postemergence biochemical maturation, it must be to the 

 details of histological and histochemical changes in the known com- 

 ponents of the insect endocrine system that we must intensify our 

 attention, in order to pinpoint the higher levels which control the 

 enzymes and related biochemical components of the uncompleted 

 target organs of the still immature imago. 



METACHEMOGENESIS IN HEMIMETABOLOUS INSECTS 



Poyarkofif's principal conclusion concerning the nature of the pupa 

 of holometabolous insects that it corresponded to the last nymphal 

 instar of hemimetabolous species was based on a considerable body of 

 evidence, chiefly from comparative morphology. If this concept of 

 the pupa as a preimaginal form similar to the last nymphal instar of 

 the Hemimetabola or more so to the subimago of the Ephemerida is 



