282 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I37 



trol of biochemical maturation in the Hemimetabola also. Mendes 

 (1948), by a thorough histological study of the corpora allata of both 

 sexes of Melanoplus differentialis (Thomas), during nymphal devel- 

 opment and adult maturation, has established a positive relationship 

 between changes in these endocrine glands (in the form of the mitotic 

 activity of its undifferentiated cells and characteristic alterations in 

 cell volume and acidophilic granule content of its secretory cells) and 

 nymphal development. At emergence of the adult, such activity of the 

 corpus allatum practically ceases ; in the adult female, thereafter the 

 maturation of the ovaries is accompanied by the rapid increase in the 

 activity of the corpus allatum to a maximum level by the end of the 

 second week after the final moult. It is of considerable interest that 

 the male corpus allatum also attains full secretory activity at the same 

 age as the female. In the latter connection, Pfeiffer's work (1945) 

 has demonstrated (for hemimetabolous forms) that the developing 

 corpus allatum of the adult (female) M. differentialis may exert a 

 generalized regulatory influence upon body metabolism through the 

 secretion of a metabolic (as well as a gonadotrophic) hormone (just 

 as Day, 1943, showed this to be true in two holometabolous, dipteran 

 species). 



THE INEQUIVALENCE OF THE MOMENT OF EMERGENCE 



That the extent of adult differentiation at the time of emergence is 

 different for different species of insects (Scharrer, personal com- 

 munication, 1956) is indicated strongly by the numerous data pre- 

 sented above. In the case of two species of hemimetabolous insects 

 mentioned, the succinoxidase activity and dry weight of the pigmented 

 thoracic muscles related to flight reach a maximum level at some time 

 between 30 and 40 days in the Madeira roach, but at only 10 days of 

 adult age in the male American cockroach. These muscles, in the case 

 of the female American cockroach, on the other hand, take about 2 

 months to reach a maximum succinoxidase content. In the Holome- 

 tabola, maturation of flight ability, in terms of maximum brain cho- 

 linesterase activity, maximum body acid phosphatase (and concomitant 

 minimum alkaline phosphatase) activity, maximum adenosinetriphos- 

 phatase activity of the thoracic flight muscles, and observed flying 

 ability all occur within 7 to 10 days after adult emergence in the case 

 of the worker honey bee. In the house fly, maximum levels of brain 

 cholinesterase, body cytochrome c oxidase, thoracic muscle adeno- 

 sinetriphosphatase, and the ability to fly are all reached at about the 

 second day. In Drosophila spp. the glycogen content, cytochrome c 



