THE INFLUENCE OF THE PHOTOPERIOD ON THE COLORADO BEETLE 

 (LEPTINOTARSA DECEMLINEATA SAY) 



Влияние фотопериода на колорадского жука 



W. WEGOREK 



(Institute for Plant Protection, Poznan, Poland) 



A discussion takes place in scientific literature on the role of different 

 factors influencing the diapause of the Colorado beetle. The reason of the dia- 

 pause луеге sought for by many factors. Tower (1917), Breitenbrecher (1918) 

 or Grison (1944, 1952) ascribed a decisive importance to temperature and 

 moisture. Fink (1925), Larczenko (1957, 1958) and Faber (1949) consider 

 food to be the decisive factor for condition of the diapause. Finally de Wilde 

 (1954, 1955), Wegorek (1955), Jermy-Saringer (1955) and Goryszin 

 (1956) draw attention to the photoperiod as a factor of first-rate importance. 



In our researches the following combinations were apphed; the Colorado 

 beetle and the potatoes serving as food were kept in a long day (18 hours), 

 a short day (11 hours) and a normal one. Besides, potatoes were grown in a dif- 

 fused light. The breeding was conducted in all combinations resulting from 

 different conditions of development of insects and plants. 



For determining different combinations the following symbols have been 

 accepted: potatoes — (P), Colorado beetle — (B), normal day — (N), short 

 day — (S), long day — (L), diffused light — (D). For feeding leaves from the 

 top were all days taken, down to the 5-th leaf inclusively. 



With the purpose of ascertaining the nutritive value of potato leaves, 

 samples were taken for biochemical analyses. 



Table 1 



Development of potatoes grown in different length of day 



231 



