METACHEMOGENESIS IN INSECTS — ROCKSTEIN 



267 



of the effects of DDT on house fly brain cholinesterase, learned that 

 the age of the fly was an important consideration in such experiments. 

 Thus, the choHnesterase activity more than doubled during the first 

 24 hours of adult life and remained unchanged thereafter for the 

 next 7 days, as is seen in table i. The accelerated development of 

 brain cholinesterase in this species (in contrast to the 7-day period of 

 biochemical maturation of brain cholinesterase in the worker honey 

 bee) parallels the equally accelerated development of flight ability in 

 the house fly within 24 hours after adult emergence. This interrela- 

 tionship of developing motor ability with maturation of maximal brain 



iO 40 50 



AGE IN DAYS 



Fig. I. — Acid phosphatase in whole body and cholinesterase in whole brain 

 homogenates of the adult worker honey bee. (After Rockstein, 1953.) 



cholinesterase activity in these two species of insects has its counter- 

 part in several important reports, in which development of motor 

 ability (locomotion) in the embryo and immature young mammals 

 (Nachmansohn, 1939; Sawyer, 1943), as well as the extent of devel- 

 opment of locomotor ability in the mature adult of each of two differ- 

 ent species of fish, amphibia, and reptiles (Lindeman, 1945), have 

 been related to the cholinesterase content of the brain and spinal cord 

 in these animals. That brain development is characterized by an in- 

 crease in cholinesterase activity was also demonstrated in the grass- 

 hopper Melanoplus differentialis by Tahmisian (1943), who observed 

 that such an increase followed secondary differentiation of the neural 

 mass, especially during the formation of ganglia and connectives, in 

 the developing embryo. 



