144 WILLIAM L. DOLLEY, JR. 



In view of the slight information available as to the effect of 

 intermittent light upon organisms other than man it seemed 

 desirable to make a thorough study of this question in some of 

 the lower forms. The mourning cloak butterfly, Vanessa an- 

 tiopa, was chosen because its reactions to light are fairly well 

 known and because it lives well in captivity and is not difficult to 

 obtain in large quantities. 



Before entering upon a discussion of these experiments I wish 

 to express my very sincere appreciation of the kindness of Professor 

 S. O. Mast whose many suggestions and unselfish aid have made 

 this work possible. It is a pleasure also to acknowledge my 

 indebtedness to Dr. H. E. Howe for the loan of apparatus and 

 for other kindnesses and to Mrs. O. F. Hiser, who supplied me 

 with the larvae from which the butterflies were reared. 



II. METHODS 



The butterflies used were all reared in the laboratory from lar- 

 vae secured from both the June and August broods in Iowa. 

 They were kept in a large wire cage, which was protected to some 

 extent by a tree which partially shaded it. They were fed upon 

 decaying fruit and a weak solution of maple syrup in water. 

 The wings of those butterflies used in the tests were clipped to 

 prevent their escape. This was not injurious, for animals with 

 clipped wings live and thrive as well as normal specimens, and 

 they behaved in the same manner. 



Two slightly differing methods were used. Those used in all 

 of the experiments, except those described in section V of this 

 paper, were as follows. The observations were all made on a 

 table in a dark room in a field of light composed of two small 

 horizontal beams, produced by two 100 Watt Edison gas filled 

 lamps, so situated that the beams crossed at right angles. The 

 lamps were mounted in front of a small opening in a light proof 

 box that was painted dead black inside. By means of screens 

 the light from these lamps was so cut down as to produce 

 sharply defined beams of the size desired. These beams were 

 the only light in the room, and this was in large part absorbed 



