PSYCHE. 



A NEW HYPOTHESIS OF SEASONAL-DIMORPHISM IN 

 LEPIDOPTERA. — II. 



BY ALFRED GOJ.DSKOROUGH MAYER. CAMBRIDGE, MASS. 



(2) iVeic Hvpotltesis of Seasonal- 

 Dim orph ism . 



I kno^v of only one experiment upon 

 the efl'ect of excessive heat upon Lepi- 

 doptera, and that was performed upon 

 the pupae of Va/icssa antiopa^ by 

 Fischer ('95) who, it will be remem- 

 bered, subjected them, when fresh, for 

 3 hours and then daily for 2-3 hours to 

 a temperature of 40°-42° C. keeping 

 them at all other times at 35°-3S° C. 

 The butterflies which issued resembled 

 those which would have resulted from 

 exposure to cold of o°-i° C. 



It has occurred to me that in this 

 remarkable fact we may have a clue to 

 at least a partial explanation of the 

 action of cold upon seasonally-dimor- 

 phic Lepidoptera. It is well known 

 from the researches of Dutrochet, Ross- 

 bach, and Plateau that if organisms be 

 subjected to gradually increasing heat 

 the metabolic processes as evinced by 

 increased excretion in protoplasm, and 

 more rapid rate of development, become 

 more and more active ; until suddenly 

 all movements cease and heat rigor sets 

 in. This is not death however for if the 

 organism be now cooled down, recovery 

 takes place, and the life processes return 



with normal vigor. According to Pla- 

 teau* the temperature of heat rigor in 

 various insects varies between 3S°-43° 

 C. It is highly probable then that the 

 high temperature of 40°-42° C. pro- 

 duced heat rigor in the pupae, and 

 therefore the metabolic processes were 

 checked, exactly as they woidd have 

 been by the benumbing influence of 

 cold. If this be true it becomes prob- 

 able that the peculiar color-aberrations 

 caused by cold are only an expression 

 of the decreased Dietabolism in the 

 pupae. It will be remembered that 

 heat of 35° C. produces an aberration in 

 V. a)ttiopa which is just the reverse of 

 that caused by cold. In this case the 

 peculiar coloration could be explained as 

 one of the results of the increased meta- 

 bolism in the pupae. 



Now it may well be that it is an advan- 

 tage to a pupa which is destined to with- 

 stand the winter's cold to i7iherit a 

 tendency toward a low metabolism, for 

 resistance to the cold would naturally 

 require the possession of low metabolic 

 processes; hence those pupae which 

 already possessed low metabolism would 



• Plateau, 

 Belgiqiie 



Bulletin d I'Acade 

 ,iv, pp. 315-317 



