SEASONAL DIMORPHISM OF LEPIDOPTERA. S5 



27th, i. e. two days before the end of the period of emergence, 

 and consequently were not subjected by a long way to the highest 

 temperature (37-38° C.) immediately before their emergence, 

 but only to a temperature of 23-29° C. 



Thirteen specimens are somewhat darker than the ordinary 

 German form. They have the black margin a little broader, and 

 the black spots somewhat larger. The black powdering of eleus 

 is also present, although generally to a very slight extent, and 

 principally on the lower half of the fore wing from the base 

 towards the band of spots only. A sharp distinction cannot be 

 drawn between these specimens and the 8 unaltered ones first 

 mentioned, and it is doubtful, whether more than 8 specimens 

 should not be reckoned in the first group. 



C. Results of the Experiments, 



The first question to be asked is : Does the temperature to 

 which the pupa is subjected affect the colour of the butterfly ? This 

 can be unhesitatingly answered in the afi&rmative. The eggs of 

 the Neapolitan butterflies more frequently produced butterflies 

 powdered with black at Naples, than when they were reared at 

 Freiburg in a room at the ordinary summer temperature, and 

 they resulted in butterflies without any black powdering, when 

 the pupse were kept at 6-10° C. On the other hand, eggs from 

 North German females of phloeas, when their pupae were subjected 

 to 24-38° C, resulted in some few specimens powdered with black, 

 which were quite similar to the Neapolitan specimens of eleus. 



It is proved by experiment 2, A and B, that the temperature 

 only produces these changes during the pupal period, and that 

 its operation during the larval period is without effect on the 

 colour of the butterfly, inasmuch as the Neapolitan larvae, which 

 were all reared at the same room temperature and first treated 

 differently during or after their pupation, produced such strik- 

 ingly different coloration in lot A and lot B. On this account it 

 was also unnecessary for the production of the summer form, to 

 keep the eggs of the German butterflies at an increased tempera- 

 ture from the beginning of and throughout the whole larval 

 period ; it was, however, necessary, in order to bring the larvae 

 to pupation in the late autumn, which, considering the small 

 number of insects available for the experiment, appeared very 

 desirable. Had the larvae been reared at a lower tempera- 

 ture, and the pupae first brought into the incubator, the result 

 would have been almost the same. In this respect the results of 

 Merrifield, which will be mentioned later on, agree. 



The second question is more difficult to answer. It is : Has 

 the effect of temperature on the colour of the butterfly become here- 

 ditary ? At the first glance this might be answered with a decisive 

 '* No," if it was taken into consideration that both in Sicily 



