400 WILLIAM L. DOLLEY, JR. 



from one point, so that the illumination of the functional eye 

 varies with every change in position of the animals. The ques- 

 tion naturally arises as to whether or not many of the reactions 

 observed under these conditions are due to this change in the 

 illumination. This was settled conclusively by placing the butter- 

 flies with one eye blackened in light so arranged that the illumi- 

 nation of all of the large portions of the uncovered eye was 

 essentially the same in all of the positions assumed by the insects, 

 i.e., in which the light was non-directive. 



To accomplish this the box described in the preceding section 

 was used. Over the top of the box there was drawn an opaque 

 cloth cover, in the center of which a circular hole, 3 cm. in 

 diameter, was cut. A 16 c.p. electric lamp was placed directly 

 over this hole in contact with the cloth. The butterfly was then 



Fig. 16 Reproduction of trail in non-directive light, 6 mc, made by butterfly 

 7/16-c (right eye blackened) immediately after the eye was covered. Note the 

 continuous turning toward the functional eye. 



placed upon the papers in the bottom of the enclosure. Some 

 light was reflected from the sides and bottom of the black box, 

 but the amount of this reflected light was comparatively very 

 small, and, moreover, it was approximately equal on all sides of 

 the animal. The luminous intensity at the bottom of the box 

 was 6 mc. 



Thirty-one butterflies were tested in this apparatus in non- 

 directive light soon after one eye had been blackened, and nine 

 were also given trials on several successive days. The behavior 

 exhibited by these animals is recorded in figures 16 and 17 and 

 in table 6. 



A study of this table and the figures show that if Vanessa 

 antiopa with one eye blackened is placed in non-directive light 

 it tends to turn continuously toward the functional eye, and that 



