course, only without the initial decrease which in the oxygen consumption is due 

 probably to the avoidance of food. Gradual growth of volume up to the time 

 of the first oviposition can be observed also in с allatum. Thus it can be 

 presumed the effectiv JH concentration is reached on the 3rd or 4th day, 

 i. e. approximately at the time of mating. 



Originally we tried to study the influence of JH implantation in fed normal 

 and castrated females operated immediately after moulting. We presumed 

 the effect of an implanted с allatum would manifest itself in the short period 

 of 3 — 4 days up to the moment when the proper с allatum reached the neces- 

 sary JH concentration. Considerable deviation due to the time of food accep- 

 tance and to its amount, however, veiled up completely the expected differences 

 even in the relatively great number of measured individuals. 



The idea how to overcome these difficulties occurred to us when observing 

 that individual differences in oxygen consumption were far smaller in starving 

 specimens; accordingly, all the following experiments were performed on such 

 individuals. The bugs starving from the time of imaginai moulting survive 

 for several weeks in the above-mentioned temperature when supplied with 

 sufficiant drinkwater and their oxygen consumption after the initial slight 

 oscillation shows a continual slight decrease. 



Johansson (1958) in his paper concerning another herbivorous bug 

 {Oncopeltus jasciatus (Dall.), fam. Lygaeidae) reports that с aUata in starving 

 females remain practically inactive and owing to that the eggs do not develop. 

 The implantation of active с allata, however, can provoke the maturation 

 of eggs even after a long starving period. These facts are valid also for the 

 species P. aptems. The starvation corresponds physiologically to the state 

 after allatectomy and is, therefore, very suitable for judging the effects of 

 c. allata implantation. 



We made two series of experiments each of them including about the same 

 number of controls. In the first one we studied the influence of implantation 

 of active с allata in normal starving females on the 3rd day after the imaginai 

 moulting. As source of с allata normal female were used in the time between 

 the mating and oviposition with distinctly swollen abdomina. In such females 

 с allata reach their maximum activity. As controls equally aged and equally 

 prepared females were used to whom under identical conditions a piece 

 of muscle was implanted corresponding in size to the implanted gland. 



In the second series we investigated the influence of с allatum extirpated 

 and implanted under identical conditions into castrated females treated all 

 in the same way. The castration was performed in nymphs at the beginning 

 of the Vth, i. e. last larval instar. The removal of the rather small о varia buds 

 at that time means unsignificant intervention into the nymphal development 

 having as consequence at the most a small retardation of the imaginai moulting. 

 Totally 200 females were operated; after a certain practice the mortality did 



148 



