DIAPAUSE IN THE COLORADO BEETLE (LEPTINOTARSA 

 DECEMLINETA SAY> AS AN ENDOCRINE DEFICIENCY SYNDROME 

 OF THE CORPORA ALLATA 



Диапауза как синдром эндокринной недостаточности 

 прилежащих тел у взрослого колорадского жука 



J. de WILDE*) 



(Laboratory of Entomology, Agricultural University, Wageningen, Netherlands) 



The conception of insect diapause as an endocrine deficiency syndrome 

 dates back to Wigglesworth (1936) who, in his studies on the regulation 

 of growth in Rhodnius prolixus Stal, observed that decapitation of nymphs 

 before the critical period causes a "status quo" condition resembling dia- 

 pause in other insects. 



Wigglesworth tentatively suggested that the chief cause would be the 

 removal of the corpora allata. Although this suggestion later on had to be 

 лvithdrawn, the idea that diapause may be the result of temporary absence 

 of hormones necessary to maintain growth has been a fruitful one. Subsequent 

 studies of Williams (1946, 1947) gave for the first time consistent proof of the 

 existence of endocrine deficiency in the brain and prothoracic glands of dia- 

 pausing pupae of Hyalophora cecropia L. 



We now have evidence that diapause in the adult Colorado beetle occurs 

 as a consequence of the inactivity of the corpora allata. 



Conditioning the adult beetle 



In former papers (de Wilde, 1955, 1958, 1959) we have shown that the 

 state of activity of the adult beetle is mainly governed by the photoperiod. 

 We have made us of this knowledge in conditioning the beetles before experi- 

 ments were made. At 25°C, a photoperiod of 10 h. results in diapause in 100% 

 of the beetle population. A 18 h. photoperiod initiates the reproductive phase 

 in 60 — 80% of the individuals. All beetles were constantly fed on young 

 potato leaves. 



Physiological effect of "short day" treatment 



A 10 h. photoperiod results in: 

 a. Intensive feeding, folloAved after 8—10 days by burrowing responses and 

 quiescence. 



*) In collaboration with Mrs. S. Maas Geesteranus, Miss L. de Boer and Mr. F. Bink. 



226 



