The experiments show c. allata of the last 1агл^а1 instar of the bug Pyrrho- 

 ooris aptenis produce from the 4th day of the intermoulting period the JH 

 in such an amount as to be capable with the aid of the host's c. allatum to 

 secrete an efective concentration of JH during the acceptor's critical period. 

 This fact is in full agreement лYith the increase of с allata volume observed 

 during the last larval instar which will be considered in another paper. 



It is interesting that even с allata of the freshly moulted imagoes proved 

 to be active, whereas the preliminary experiments with imagoes on the three 

 first days after moulting gave negative results. The function of с allatum 

 during the moulting demands of course a more detailed analysis. It seems, 

 hoAvever, that the species P. apterus does not need any nervous impuls to start 

 the activity of c. allata, in contradiction to the blood sucking species 

 Bhodnius prolixus, as shown by Wiggles worth. This corresponds to the 

 analogical conditions valid for the activation hormone. As Wigglesлvorth 

 (1936, 1940) showed in Bhodnius prolixus the secretion of the activation 

 hormone is induced by a nervous impuls given by a definite grade of expansion 

 of abdomen of the blood-sucked specimen. The same лvas ascertained by 

 Dëtinovâ (1954) in Anopheles macuUpennis Meig. Pyrrhocoris apterus, hoAvever 

 is able to develop and moult without the expansion of abdomen by food 

 (Novak 1951 b). It can be supposed that the с allatum of the blood-sucking 

 species has been secondarily adapted and, therefore, the state in P. apterus 

 appears to be the original one. 



To exclude the possibility of an accidental peculiarity occuring in P. apterus 

 only (perhaps because of its slight neoteny manifested by the brachypterous 

 condition) we repeated the experiment with the species Galleria mellonella (L.) 

 As source of с allatum we used caterpillars taken out of coccoons, i. e. on the 

 5th — 1st day preceding to pupation. Out of 95 pupated individuals 9 (9-4 p. c.) 

 exhibited a distinct area of larval cuticle in the place of implantattion. In one 

 instance a typical pupal cuticle without scales developed in the moth after 

 the imaginai moulting. 



On the basis of the described experiments it can be stated that the JH 

 production in с allata continues during the last larval instar of insects лvith 

 metamorphosis as it has been supposed by the gradient-factor theory. Of course, 

 by this fact we do not mean to express a sceptical attitude towards the results 

 of the above mentioned authors. There was already mentioned the specific 

 dependence of the production of metamorphosis hormones on the nervous 

 impulses obtained by the expansion of abdomen in Rhodnius prolixus. This 

 feature has a clearly adaptive character in the blood sucking animals (saving 

 of reserve substances through inhibition of the moulting process during the 

 period of scarce food) and seems to be the cause of a different functioning 

 of c. allatum in this species, 



1 55 



