ENDOCRINOLOGY OF INSECT DIAPAUSE 14] 



DISCUSSION 



Galun: Does Carrol Williams' experiment mean that H. 

 cecropia does not need any gonadotropic hormone for egg 

 maturation? 



Lees: That is so. The control of egg development by hormone 

 varies greatly in different insects. Ccilliphora requires material 

 from the neurosecretory brain cells for egg development. Many 

 require juvenile hormone from the corpus aUatiim, but H. 

 cecropia pupae will develop viable eggs after removal of the 

 corpora allata. The puzzling thing is that the corpora allata of 

 male H. cecropia adults produce large quantities of hormone 

 which the moth does not appear to require at all. 



Galun: Is it possible, in your experiment with aphids, to 

 illuminate the internal organs directly rather than through the 

 epidermis, and get the same effect? 



Lees: It would be very difficult technically, since the aphids 

 must be allowed to feed freely on the host plant after each cycle 

 of illumination. 



Pener: What is your opinion on Bodenstein's experiment on 

 the disappearance of the thoracic gland after the last moult in 

 the adult cockroach? But when the corpora allata had been 

 extirpated the thoracic gland remained intact and extra moulting 

 of the adult occurred. 



Lees: As in other insects, attainment of the adult state in 

 Periplaneta is accompanied by the degeneration of the thoracic 

 glands; and this is the immediate reason for the cessation of 

 moulting. Bodenstein has shown that, under experimental 

 conditions, the thoracic glands can be caused to remain active 

 in the adult, and the adult then moults. The necessary conditions 

 for preserving the thoracic glands seem to be satisfied when the 

 corpus cardiacum is active and the corpus allatum inactive. 



Shulov: I should like to refer to an experiment made on 

 larvae of Trogoderma granaria. One set of larvae continued to 

 moult over a period of eight months becoming gradually smaller 

 until they became microscopic. The other set did not moult at 



