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a graduated series of more or less perfect models was made, 

 diñering in size as well as in colour and markings from the real 

 butterfly. Among them were pictures which, although perfectly 

 agreeing with charlonia as to colouring and pattern, were thrice 

 the size. While these also attracted a few single males, the 

 latter approached only for an instant and then passed on again, 

 whereas in the case of exact models they remained a considerable 

 time, attempting to copulate, and often returned several times 

 if, being defeated in their purpose, they had flown away. 



Another series of paper models, while exactly corresponding 

 to the real butterfly in size and markings, showed dift'erent 

 colours. Here it was noticed that the lemon-yellow males 

 always sought out ñrst the lemon-yellow model, and only after 

 finding their efforts in vain, would turn also to differently 

 coloured ones, but in this case only to those which were of a 

 colouring that the human eye also perceives as similar to the 

 colouring of the butterfly, viz. white and pale orange. Brown 

 models had, however, no attraction for them whatever. 



It now remained to be seen whether perhaps other senses 

 played some part in bringing about the recognition. The paper 

 models having, during the first series of experiments, been 

 brought to the place in a box which a few days before had con- 

 tained a female of the species in question, it was thought 

 possible that they might have become impregnated with its 

 peculiar odour and thus be rendered attractive to the males. 

 In order to make sure of this, a new set of models was made 

 and carried to the place in a note-book. As they produced 

 precisely the same effect as the previous ones, we may safely 

 eliminate the sense of smell. 



After thus having established the possession of the sense 

 of colour and size, the author proceeded to test the abilit}' of 

 the butterfly to judge form and pattern. In A. charlonia copula- 

 tion takes place in such a way that while the female sits with 

 expanded wings upon a stone, the male, hovering close above 

 it with a fluttering motion of the wings, repeatedly descends 

 quite suddenly upon the back of the female, keeping all the 

 while its head and body parallel to that of its mate. 



After the model had thus been kept for some time in the 

 natural position, with its head slightly erect, it was now turned 



