Table 6 



Prolificness of 100 females (Larvae bred in different 

 combination, beetles in normal days and on normal food) 



Table 7 



Prolificness of 100 females (The larvae bred in a normal day 

 and on normal potatoes, the beetles — in different combinations) 



The receptacles of the himinous stimuH manifesting themselves later as 

 a photoperiodical reaction are here most probably the organs of sight, similarly 

 to other insects, which fact was proved by Gejspic (1949, 1957) in her papers. 

 According to de Wilde (1954, 1955), the mechanism of action of the photo- 

 period on the Colorado beetle consists in inciting a hormone secretion through 

 corpora allata. This author has stated that corpora allata of active beetles 

 are considerably larger than those of beetles in diapause. A short day checks 

 the secreting activity of those bodies, a long day incites them to secrete 

 hormones. As the creation of the yollv in the ovary of insects of different 

 species is only possible in the presence of a hormone produced by corpora 

 allata, the luminous stimulus has a decisive importance for prolificness. 

 In our researches we have ascertained quite distinctly the justice of this view. 



As the development of the Colorado beetle in the natural conditions of 

 countries of moderate climate proceeds in days of different length (from May 

 to September) the photoperiod must play an important role. 



LITERATURE 



Breitenbecher J. K., 1918, Cornegie Inst. Publ. 427. 

 Faber W., 1949, Pflanzetbschutzberichte., 3. (5/6) : 65—94. 

 Fink D. E., 1925, Biol. Bull. Mar. Biol. Lab. T., 19 (5). 

 Gejspic K. F., 1949, Dokl. Akad. Nauk SSSR, 68(4): 781—784. 



— 1957, Entom. Zumal, 34: 548—560. 



Goryszin N. I., 1956, Dokl. Akad. Nauk SSSR, 109: 205—208. 

 Grison P., 1944, С R. Ac. Sei. Paris, 1944: 342—344. 



— 1952, Trans. 9. Int. Congr. Ent. Amsterdam, Vol. 1 pp. 331—337. 



235 



