102 THE ENTOMOLOGlS*. 



ON THE CAUSES OF VARIATION AND ABERRATION IN 

 THE IMAGO STAGE. OF BUTTERFLIES, WITH SUG- 

 GESTIONS ON THE ESTABLISHMENT OF NEW 

 SPECIES. 



By Dr. M. Standfuss, Lecturer in both Academies at Zurich. Trans- 

 lated by F. A. DixEY, M.A., M.D., Fellow of Wadham College, 

 Oxford. 



(Continued from p. 76.) 



III. The Pupa. 



Degrees of temperature and of humidity are in this case the 

 only influencing conditions as to which anything can be said. 

 Nevertheless the very numerous experiments which I have for 

 some years conducted on the pupae of a series of species, and 

 moreover on large numbers of individuals of each species, with 

 regard to the influence of varying temperature, have led to most 

 remarkable results. I can truly say that during the period of 

 more than twenty-five years which I have devoted to practical 

 biological studie-i in entomology, I have never had before me 

 anything approaching the astonishing results to which I am now 

 referring. Can it be called anything but astonishing that it 

 should be possible, by means of a simple experiment, to make 

 larvas of P. machaon, collected near Zurich, develop into a form 

 of the perfect insect such as that which flies in August in Syria, 

 perhaps near Antioch and Jerusalem ? Or that from German 

 and Swiss pupae of Vanessa a-ntiopa, L., by the action of well- 

 defined factors, there should be produced an imago which in part 

 comes very near to the Mexican V. cyanomelas, Doubl. Hew. ? 

 Or to force at will the one half of the progeny of one and the 

 same female V. cardui, L., to develop into a form of the perfect 

 insect almost identical with that occurring in the German 

 possessions in Africa, and the other half to assume an aspect 

 like that of V. cardui at the northernmost limit of its range, for 

 instance, in Lapland ? And apart from these glimpses into the 

 causes of the variation of species, and into the nature of the 

 species as such, a vista also opens out of the very relations of 

 affinity, of the conditions of phylogeny, and of the derivation of 

 one species from another. 



In the collection of my father, who left me ten years ago all 

 he had in the way of Lepidoptera, I possess a pair of V. ,ab. 

 porima, 0., the intermediate form between V. levana, L., and V. 

 prorsa, L., labelled "Magdeburg, 1852; pupre kept in cellar." 

 The fundamental idea of the following experiments is therefore 

 substantially forty years old, even if a still earlier date should 

 not be forthcoming from some other quarter. I know of no 

 publication on this subject reaching back so far as the fifties* 



