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ON THE SENSE OF VISION IN INSECTS. 



By A. Seitz, Darmstadt. 



Pursuing the question of "How do insects see the world?" 

 my experiments lead me to conclude that the eyes of many 

 day-flying insects perceive outlines as well as colours in exactly 

 the same manner as, judging from their visible actions, we are 

 forced to assume in vertebrates and man. 



In order to prove whether diurnal butterflies are led by 

 their sense of vision or, as is the case with most Heterocera, 

 by smell, I employed models of certain butterflies made of 

 coloured paper, which I exposed in places where I knew 

 males of the same species had to pass when hunting for the 

 females. Thus I noticed at El Kantara, in Algeria, that the 

 top of a range of hills frequented by a yellow, black-margined 

 butterfly, Anthocharis char Ionia Dup., was the meeting- place 

 of the males, who came here from great distances to mate. 

 Exposing in this place one of the paper butterflies, which I 

 fastened with a pin on the ground, often as many as six males 

 were seen trying at the same time to copulate with it. The 

 maximum distance at which they were attracted was about 

 2^ metres (= 8 ft.) ; beyond that the paper model did not 

 seem to have any visible influence. 



Moreover, it was plain that the sham butterfly was clearly 

 recognised, for when pictures of other species were substituted 

 they were completely ignored. Thus a paper model of Pararge 

 megcera, which species flies in the same place, had no influence 

 whatever upon the Pierid ; on the other hand, the more exact 

 the resemblance of the model was to the butterfly A. charlonia, 

 the more intense and lasting was the effect produced upon the 

 males. 



In order to test the acuteness of their sense of recognition 



