XXXV 



the pupae of the South American Papilio Polydamas L. of which species it 

 has been stated by Fritz Muller that they are dimorphic as regards colour 

 and that both green and brown pupae occur. Also concerning the pupa of 

 the European Papilio Machaon L., which is likewise dimorphic, produces 

 green and brown pupae and similarly has not shown any symptoms of this 

 susceptibility. Various investigators have experimented with it in this connection. 

 I find it noted by a certain German observer that green as well as brownish- 

 grey or plain grey pupae occur in this species, some of the first named having 

 dark markings — all irrespective of the surrounding amid which pupation took 

 place, with this qualification, that those reared in a dark case, although showing 

 both the colours named, were in general somewhat darker. Cecil Floersheim, 

 in an essay entitled " Some 7iotes on the earlier stages of Papilio Macliaon, parti- 

 cularly with regard to the colour-dimorphism oj its pupa " occurring in The Ento- 

 mologist's Record and Journal of Variation, vol. xvii, {igo^), came to a different 

 conclusion. According to him the green pupae were formed almost exclusively 

 between green leaves but a few (2 to 11 5) against dark-brown twigs near the 

 soil, while on the other hand the brown ones occured mostly against these 

 dark-brown twigs and a few against green leaves but not against the light green 

 ones where the majority of the green pupae were found. Some fifteen, having 

 pupated against wood painted white and being exposed to the full glare of the 

 sun, were all brown and he, therefore, while admitting the influence of the green 

 leaves, does not consider that bright light promotes this adaptation. 



Many similar observations are mentioned in the work by Wilhelm Petersen 

 " Zur Frage der chromophotographie bei Schmetterlingspuppen {18 go)" which, 

 however, are on the same lines as the others already referred to. 



On quietly passing all these observations in review, ignoring for prudence 

 sake the first mentioned in which a strong desire is manifested of seeing what 

 the theory of mimicry suggests finding and provisionally also passing by the 

 quasi-alchemic ones of Poulton — to which I shall refer later — it appears 

 to me that they may all be summed up as establishing some amount of darkening 

 as the result of a dark environment or at least an environment making that 

 impression on the larva. This result being invariably in relation to the colour 

 which obtains normally in the species, as well as to the susceptibility to the 

 accompanying stimulus which always differs in each individual and to which is 

 due the fact, so astonishing to most observers, that experiments conducted 

 exactly in the same manner on various individuals not only differ somewhat but 

 show directly opposite results. In this manner the considerable difference of 

 temperature in the experiments related by Standfuss may possibly have occa- 

 sioned difference in susceptibility. 



