XX 



have to accept several species, the transition from race into species can only 

 date from rather recent times. For this reason the wings of this genus show 

 a pattern-book of the gradual, but always very irregular i)rogress of this 

 evolution, as is not so characteristic elsewhere. But also in many species 

 belonging to other genera this process is very obvious, especially so in the 

 family of the Pieridae. And this study is indispensable for the knowledge of 

 the morphology, especially among the Lepidoptera. Studies concerning these 

 insects, when we are ignorant of the said phenomenon or if we do not take 

 it into consideration, do not answer any more to the requirements that are 

 expected of scicntifical labour. 



Man)' species of Rhopalocera only occur at certain altitudes above the sea, 

 others show at different altitudes variations in form and colour which are also 

 often due to the greater humidity in the mountains or to some other suchlike 

 influence which affects their early stages. Sometimes also separate races have 

 been formed in certain regions ; then it also happens that afterwards such a 

 race is again dispersed over a district where the not yet changed form still 

 exists, or that on the contrary this latter one spreads where a new race has 

 sprung up, and then the two forms occur there beside each other, at least till 

 gradually by mixing together and by the progress of the evolutional change 

 the two have again become the same. The altitude at which the butterflies 

 have been found is, therefore, as far as I knew it, always mentioned by me 

 in metres, by a figure in brackets. 



In ignorance of the fact that the ever varying manner in which the pig- 

 mental coloration occurs among the Lepidoptera, is mainly the effect of an 

 evolutional process connected with it, and consequently in the erroneous idea 

 that only external influences govern it, endeavours have been made by numerous 

 experimental researchers to confirm this meaning, especially the supposition 

 that heat and cold cause such variations. Moving entirely in the narrow-minded 

 sphere sprung from the generally exclusive knowledge of the European fauna, 

 people quite forget that if the great change of heat and cold in Europe may 

 be of significant influence, this cannot very well be the case in the tropics and 

 that if therefore — as indeed occurs — tropical butterflies normally show exactly 

 the same changes of colour as the European ones, the cause of this must 

 probably in the latter not be attributed to these influences either. Neither do 

 these variations depend on the pretended differences of the dry and the wet 

 season, which have been represented in an exaggerated manner. 



Some acceleration or delay in this process has been brought about along an 

 experinental way in butterflies from the temperate zone, whose progress in their 

 evolutional change under normal conditions is more or less connected with 



