1672 THE BUTTERFLIES OF NEW ENGLAND. 



hut not pattern except in the vaguest way. The comparative experi- 

 ments revealed an enormous clifFerence in the behavior of vertebrates and 

 insects under precisely identical circumstances ; the former acting as if they 

 possessed human vision, the latter as if they could distinguish the form 

 and boundaries of objects in a most imperfect way, at the best. 



"A flying insect," says Plateau at the conclusion of his various experi- 

 ments, "has a very lively perception of light and shadow, so that without 

 distinguishing as we would do all tlie details of its route, it knows how to 

 avoid all masses such as the trunks of ti'ees, bushes, rocks, walls, etc., and 

 passes them at a con\-enient distance. Caught from any cause in a mass 

 of shrubbery or any other group of vegetation, it takes advantage, when 

 it wishes to pass on, of those passages through which the greatest amount 

 of light filters or, as between two equal in this respect, of such as seems 

 to it to offer the most room. If the wind move the leaves, these openings 

 maj' oscillate, but thanks to its good perception of movements, the insect 

 can then see them better. In flying, the insect moves in undulations so as 

 to follow the direction of the displacements and to traverse the openings 

 without striking. 



"When its mode of sustenance necessitates a visit to cei'tain flowers, it 

 moves toward them either with certainty, in being guided by its sense of 

 smell only, if its power in this direction is well developed ; or by chance, 

 if its olfactory powers are relatively slight. Incapable of distinguishing 

 by their forms flowers of the same color, it goes directly toward the 

 colored spots which to it mean corollas or inflorescence, turns, hesitates, 

 and does not decide what to do until the distance has become sufliciently 

 sli<Tht to enable it to determine by the odor whether or not it has found 

 what it seeks. 



"The sense of smell only or this combined with visibility of movements 

 assures the meeting of the sexes, and finally it is the perception of move- 

 ments which warns of the approach of an enemy and permits escape in 

 time. 



"This brief statement is sufficient to show how an insect with facetted 

 eyes, though it only has a confused visual perception of objects at rest, 

 frequently acts in a manner to suggest to one who does not closely 

 analyze the phenomena that the eyesight of these creatures is as distinct 

 as that of the vertebrates." 



The consequences of such a conclusion are far-reaching. It follows 

 that the whole structure upon which the theory of sexual selection in 

 insects has been based is at fault, and it supports the objections to it which 

 Wallace has brought on other grounds. It shows that the recognition 

 of the food plant by the mother, which does not and cannot taste it, must 

 be by some other sense than that of sight. And it becomes clear that 



