DIAPAUSE AND INSECT PHENOLOGY 157 



impending crisis affecting its development (oncoming winter 

 cold in the temperate zones, or the approach of dry summer in 

 the semi-arid zones), must be communicated to the insects 

 consuming those plants. In other words, either diapause- 

 inducing or development-inhibiting substances are to be sought 

 in the diet of insects, especially those exhibiting facultative 

 diapause. This should be a mechanism somewhat similar to that 

 of the response to the host in parasitic insects, although Dr. Lees 

 will probably argue that the latter is a case of quiescence rather 

 than of strict diapause. 



Before concluding I should like to raise briefly one more 

 point. One might be highly tempted to try to dismiss the whole 

 issue by the trite argument that we are dealing with quite 

 distinct geographical or ecological races of the species; in the 

 case of the codling moth different names have even been given, 

 viz. Putaminana Stdgr. for the Near Eastern race. It might in 

 turn be argued that each of these races hereditarily responds to 

 a certain consistent environmental agency, whether as regards 

 the onset of diapause or its termination, and not to alternative 

 agencies, according to the different environments. Allow me to 

 avert these temptations by quoting a few lines from an article 

 written by Bodenheimer and Vermes^- some three years ago: 

 'Diapause depends upon the interplay of heredity and environ- 

 ment. Hence, no general genetical solution of the problem of 

 diapause determination can possibly be given. Once the one, 

 once the other factorial group may be the main inducing factor. 

 Yet even under apparently similar environmental conditions 

 during the critical period or in populations of an apparently 

 higher homogeneous genetical constitution may result as 

 different phenotypical manifestations.' 



REFERENCES 



^ A. D. Lees, The Physiology of Diapause in Arthropods, Cambridge Uni- 

 versity Press, London, 1955. 

 - E. RivNAY, Proc. 10th Intern. Congr. EntomoL, Montreal, 2 (1958) 743. 

 ^ L. BoNNEMAisoN, Ann. epiphyt., 11 (1945) 19. 



