On the Seasonal Dimorphism of Butterflies. 2 7 



into the Prorsa form. I have repeatedly exposed 

 a large number of Levana pupae of the third 

 generation to the temperature of an apartment, or 

 even still higher (26 R.), during winter, but no 

 Prorsa were obtained. 17 



But it would be erroneous to assume a difference 

 in the action of heat according as it began on the 

 first or third day after transformation ; whether 

 during or before pupation. This is best proved 

 by Experiment No. 12, in which caterpillars of 

 the fourth generation were placed in the hothouse 

 several days before they underwent pupation ; 

 still, not a single butterfly assumed the Prorsa 

 form. I have also frequently made the reverse 

 experiment, and exposed caterpillars of the first 

 summer brood to cold during the act of pupation 

 A regular consequence was the dying off of the 

 caterpillars, which is little to be wondered at, as 

 the sensitiveness of insects during ecdysis is well 

 known, and transformation into the pupal state is 

 attended by much deeper changes. 



Dorfmeister thought that he might conclude 

 from his experiments that temperature exerts the 

 greatest influence in the first place during the act 



17 When Dorfmeister remarks that hibernating pupae which, 

 at an early stage " were taken for development into a room, or 

 not exposed to any cold, gave dwarfed, weakly and crippled," 

 or otherwise damaged butterflies, this is entirely attributable to 

 the fact that this able entomologist had neglected to supply the 

 necessary moisture to the warm air. By keeping pupae over 

 water I have always obtained very fine butterflies. 



