COLE. — IMAGE-FORMING POWERS OF VARIOUS TYPES OF EYES. 381 



"4. Its positive phototropism occurs with lights varying in inten- 

 sity from 2 candle-power at 2 meters distance (0.5 candle-meter), t) 

 250 candle-power at 2 meters distance (62.5 candle-meters). . . , 



" 10. V. antiopa does not discriminate between lights of greater oi 

 less intensity provided they are all of at least moderate intensity and 

 of approximately equal size. 



"11. V. antiopa does discriminate between light derived from a 

 large luminous area and that from a small one, even when the light 

 from these two sources is of equal intensity as it falls on the animal. 

 These butterflies usually fly toward the larger areas of light." 



It will be seen that Parker had already concluded what might be ex- 

 pected to result from experiments on these butterflies under the con- 

 ditions of the present investigation. His conclusions were based in 

 large part upon observations in the field, supplemented by a number 

 of experiments conducted in the laboratory. These, while they seemed 

 to establish the verity of his conclusions beyond a reasonable doubt, 

 were largely qualitative in their character, and it seemed of interest 

 to repeat them under conditions in which the intensities and compara- 

 tive areas of the lights were accurately known. Specimens of V. a?itiopa 

 were accordingly procured, and as it was desirable — considering the 

 comparatively small space where the insects could be exposed equally 

 to the two lights — to have them crawl instead of fly, the wings were 

 clipped off a short distance from the body, leaving only short stumps, 

 by means of which the animals could be easily handled. Two difficul- 

 ties presented themselves. Many of the butterflies either made at- 

 tempts to fly, which resulted in their flopping about helplessly on the 

 table, or they feigned death when released and refused to move at all. 

 It was found that by holding the animal by one wing-stump, it would 

 usually struggle with its legs and the other wing-stump. If in such 

 a state of activity it was placed on the table, it would seldom feign 

 death, but would start at once to crawl off. Attempts to start the 

 animals with exact orientation in the normal position were abandoned, 

 since it was found that holding them by one wing was apt to impart 

 a unilateral impetus to their first locomotor movements ; furthermore, 

 after starting to crawl they would often begin making attempts to 

 fly, and so struggle about on their backs with their legs in the air, 

 thus losing all orientation before they regained their feet and pro- 

 gressed again by creeping. For similar reasons no record was made 

 of the angles at which the animals diverged from the normal ; in fact, 

 when they once began crawhng well, they crawled, as a usual thing, 

 directly toward the light. In some cases they would first crawl a 

 short distance toward the small light and then turn and go toward 



