implanted corpus allatiim, л\а11 start producing eggs even when fed onh' on 

 glucose. 



In this way it has so far been possible to demonstrate that a corpus allatum 

 may remain active and be able to induce egg production in glucose-females 

 even after having been transplanted into four successive generations of females. 



The mechanism лу111с11 probably is operating in Oncopeltus, is that in starved 

 or glucose-fed females, the corpus allatum is inhibited or restricted in its activity 

 by the central nervous system, notably the brain. The restraining influence 

 of the central nervous system is mediated through the nervous connections 

 which exist between the corpus allatum and the ganglia in the head. An indic- 

 ation that this is so, is the fact that it is actually not necessary to implant 

 a foreign corpus allatum in a starved or glucose-fed female to induce egg 

 production. Similar ovarial activity is obtained if we denervate the corpus 

 allatum of a newly emerged female, either by cutting the nervous connections 

 to the organ, or by extirpating the main regions from which these nerves 

 originate, that is the dorsal part of the brain. We must assume that after the 

 denervation, the central nervous system cannot longer exert any restraining 

 influence over the corpus allatum and the autonomous activity of the organ 

 becomes evident. This raises the hormone titer to a 1ел^е1 high enough for 

 egg production. In the normal sequence of events this restraining influence is 

 broken by the uptake of adequate food. This normal activation and growth 

 of the corpus allatum can, howeл^er, only manifest itself if the organ has its 

 nervous connections with the central nervous system intact. 



It is very interesting to note that conditions similar to those here demon- 

 strated in Oncopeltus, are found, not only in other insects (Harnack, 1958), 

 but even in mammals. In mammals both inanition, reduced caloric intake 

 or diets deficient in proteins, impair the gonadotropic secretions of the pituitary 

 and can thereby completely halt reproduction. The reproductive organs of 

 starved individuals are, however, capable to respond to the administration 

 of pituitary material. 



Both in insects and in mammals reproduction is a strain on the individual 

 of many species. This mechanism therefore ought to be of importance in in- 

 creasing the chances of survival for the individual under conditions Avhere the 

 required quantitites of adequate food is not available. In fact it has proved 

 possible to obtain certain informations on this point from the following experi- 

 ment in Oncopeltus. 



During the first day after emergence, female individuals received an implant- 

 ation of either Ringer's solution, or a corpus allatum taken from a newly 

 emerged female, or a corpus allatum taken from a sexually mature female. 

 The individuals were starved to death and the number of eggs produced луеге 

 counted. It was found that the 10 females \vhich received an injection of Ringer's 

 only, survived for an average of 10-8 days and produced none eggs. The 6 fema- 



135 



