VANESSA ANTIOPA LINN. 461 



180°, came to rest in the characteristic negative position. After a few minutes I made 

 it creep again in the sunlight, but this time it merely crept toward the light and failed 

 to orient negatively. I soon learned, by repeating this experiment on three other 

 butterflies, that the state of irritability, in which negative orientation takes place in 

 consequence of exercise, is of very brief duratibn. For, though I could bring it about 

 often by only two or three excursions, instead of five, I seldom found it to last more 

 than a few minutes. Nevertheless the experiment made clear to me that the nega- 

 tive phototropism of this species, as shown in its position of rest, is dependent not 

 only upon strong sunlight, but also upon previous vigorous exercise, whereby, doubt- 

 less, a state of metabolism is established different from that of the resting insect. 



These observations give some support to the opinion of Loeb that there is a 

 rhythmic change in the state of a butterfly, and that this change influences its photot- 

 ropism. But in V. antiopa the response involved is a negative one, whereas in the 

 case observed by Loeb it was positive. My observations, however, give no support 

 to Loeb's idea of a daily rhythm that controls phototropism; in fact I found, as had 

 already been observed by Scudder (74), Murtfeldt ('84), Edwards ('85), Howard 

 ('93, '99), and others, that butterflies liberated a't night fly toward a lighted lamp as 

 they do in the day. Neither do my observations give support to Davenport's con- 

 tention, that butterflies are attuned to light of only great intensity, for, at least in 

 V. antiopa, the individuals will congregate about the dim light of a candle or lamp, 

 as well as about a strong arc light; in this respect they are precisely like moths. 



It is not unnatural to ask why V. antiopa orients negatively when it comes to 

 rest in sunlight, though in all other light reactions it is positive. One very striking 

 accompaniment of its negative orientation is the spreading of its wings. When a 

 butterfly orients in the sunshine it almost invariably spreads its wings, and they are 

 as a rule kept open unless the insect is disturbed by an observer or by a lengthy with- 

 drawal of sunlight. Under these conditions the insect is likely to close its wings and 

 remain an inconspicuous object until the disturbance has ceased. But when it is 

 undisturbed in the sunlight, the wings are usually kept broadly open and the fore- 

 and-aft slope that they have exposes them much more effectually to the bright light 

 than would be the case if the insect were oriented with the head toward the source 

 of light. They thus are placed in a position of extreme conspicuousness, so far as 

 the wing patterns are concerned, and since the imago is the stage in which the sexes 

 pair, I am inclined to believe that the position described is one taken for display, as 

 a means of bringing males and females together. I have been, however, unable to 

 find any differences between the sexes in respect to orientation, for males and females 

 orient alike, and I am sure from direct observations that females, as well as males, 



