156 PRINCIPLES AND CONCLUSIONS. 



females of Pieris, recognizing them as different by their staccato flight and 

 large white surface. It was concluded that the observations given for this 

 one species, belonging apparently to those better endowed mentally, show 

 how necessary it is to distrust statements as to the perfect clearness of the 

 vision of Hymenoptera. 



Admiration of syrphids for bright flowers. — In the third and last 

 paper of this series (1900:266), Plateau discussed the current views as to 

 the admiration exhibited by syrphids for bright-colored flowers. To refute 

 this view he listed 35 species with green or greenish flowers for which charac- 

 teristic visits by syrphids were recorded, and gave a large number of obser- 

 vations in which species of Syrphus in particular hovered in the usual 

 fashion over leaves and other objects. In addition, he showed by experi- 

 ment that these flies could be made to respond as usual by means of a 

 variety of objects, such as a finger, the tip of a cane, etc., His conclusions 

 were as follows: 



(1) The number of cases clearly described of supposed shows of admiration for the 



color of flowers is very limited and may be reduced to seven altogether out of the 

 thousand described by naturalists. 



(2) The only insects noted are the dipterous syrphids, with limited faculties inferior 



to those of the bees. 



(3) The syrphids regularly exhibit their so-called admiration before flowers not only 



without bright colors, but also before green and greenish ones. 



(4) They frequently hover before other plant parts than flowers, such as green leaves, 



green buds, and fruits, green and brown stems. 



(5) Syrphids also exhibit their characteristic stationary flight before objects having 



no resemblance to flowers, such as a finger, a cane, a marble, or a string. 



(6) As a consequence, admiration for the color of flowers does not exist among insects. 



Attraction of colored cloths and brilliant objects. — Plateau em- 

 ployed banner-like pieces of colored cloth to determine the attraction of 

 color when not associated with flowers (1900 2 : 174). In the first experiment 

 the colors used were bright red, yellow, bright violet, and sky-blue, the 

 cloths being suspended on leafy branches at about a meter above the soil. 

 The sole response to the banners was made by a single individual each of 

 Musca, Calliphora, and Megachile, which seemed to rest on the yellow cloth 

 as on any object. However, 7 individuals of Eristalis and 1 honey-bee 

 hovered over a fringe of blue wool. The position of the colors was then 

 changed, but the results were similiar; Pieris was attracted slightly by the 

 blue, one Eristalis and Bombus rested on the violet piece, while 11 Eristalis, 

 4 Syrphus, and 1 Pieris hovered over the blue fringe. Two further tests 

 were made with much the same results, the entire series yielding 30 cases 

 of probable and 8 of doubtful attraction. All but 2 of the first were caused 

 by the blue fringe, as well as 4 of the latter. Of the total, 5 visits were made 

 by bees, 29 by flies, chiefly syrphids, and 4 by buttei flies. 



To determine the effect of brilliant objects, four spheres of metallic 

 luster and 4 to 6 cm. in diameter were employed. One of these was red 

 above and blue below, the second had these colors reversed, while the other 

 two were glass silvered within. These were suspended on stakes at the 

 usual height of the flowers visited. All told, there were 24 cases of evident 

 attraction and 10 doubtful ones, the silvered spheres furnishing 14 of the 



