408 PKOCEEDINGS OF THE AMERICAN ACADEMY. 



those of the present investigation, however, we are able to give another 

 and, it would seem, a more reasonable explanation. The moths and gnats 

 referred to react, like Vanessa, to large areas of light rather than to a 

 point of more intense light. As a consequence they remain near the 

 ground, on account of the bright patches of moonlight, instead of flying 

 toward the moon itself. If, however, they come close to a candle, its rel- 

 atively great intensity at so short a distance may overcome the reactions 

 to the moonlit areas, and the insects accordingly fly into the flame. 

 This is especially the case, as recorded in the note, when the moon 

 is obscured by a cloud and the patches of moonlight disappear. 



Parker (:03, p. 461) has pointed out, furthermore, that the alighting 

 of Vanessa in sunny spots with the wings expanded is probably an 

 adaptation which serves to bring the sexes together ; for it is in this 

 position, headed as it always is away from the sun, that the colors 

 and markings of the upper surfaces of the wings are most conspicuous. 

 He adds, "I am sure from direct observations that females, as well as 

 males, will circle around an oriented and expanded individual of either 

 sex, till both fly off together." The recognition by one butterfly of 

 another as a definite object in its field of vision indicates a much finer 

 perception than that which distinguishes merely the diff"erence of size 

 in illuminated areas, and approaches to the highest type of vision. 

 Although no experiments were made which bear directly upon this 

 point, it is, nevertheless, worthy of brief consideration. 



Nuel (: 04) speaks of "la perception simultanee des fins details des 

 objets visuels " as " iconoperception" (p. 82), and of the resulting re- 

 actions as " icono-rdactions." ^^ He says (p. 83): " Chez les animaux, 

 nous ne parlerons pas d'iconopsie, mais d'icono-rdactions, dans la cas 

 ou, comme chez I'homme, des mouvements sont suscitds ou guid(^s, 

 rdglds par les fins details visuels des objets." As the perception of 

 the details of the objects in the general image of the visual field be- 

 comes more refined, the reactions to these objects, or to certain partic- 

 ular ones of them, appear largely to inhibit the reactions to light in 

 o-eneral, including that to large areas as contrasted with small. Besides 

 the case of Vanessa, mentioned above, it seems certain that many 

 Lepidoptera and bees react to certain flowers, while many predacious 

 insects, such as the dragonflies, are remarkably quick in detecting their 

 prey. That color is not, in all cases at least, the determining factor in 



" The words ironotropism and iconotaxls would oorresi)ond with tlie terms more 

 generally employed, such as phototropism and phototuxis, and miy,ht be employed 

 to designate specifically the reactions of animals to areas of light and to objects 

 in the field of vision, in contradistinction to reactions to the intensity of the 

 licht. 



