508 WILLIAM L. DOLLEY, JR. 



METHODS 



The experiments in which continuous illuminations differ- 

 ing in strength were used may be designated as experiments 1 

 and 2. 



All the experiments were performed in a dark room. In 

 experiment 1 the insects were tested alternately in light from 

 a 36 c.p. automobile lamp and in direct sunlight reflected into 

 the room by mirrors. In experiment 2 they were tested in 

 light from the 36 c.p. auto lamp at different distances. A 

 table 300 cm. long, covered with rough black cardboard, was 

 divided into 20 equal spaces, each 15 cm. wide, by means of 

 white threads stretched across the table and lying directly upon 

 the cardboard. At one end of the table was placed a mirror 

 upon which was thrown the desired beam of light, and from 

 which emanated a horizontal beam, about 20 cm. wide, which 

 extended the length of the table. Between the edge of the 

 table and the mirror was placed a glass vessel with parallel 

 sides, 3 cm. apart, filled with distilled water to eliminate heat 

 effects as far as possible. 



The wings of all of the butterflies used were clipped. The 

 insects to be tested were placed in the beam at the far end of 

 the table and facing the mirror. They soon started to proceed 

 toward the light. As they reached each white thread the ob- 

 server gave a signal which was noted by an assistant in another 

 room. By the aid of a stop watch this helper kept an accurate 

 record of the time taken by each insect to traverse the spaces 

 between the threads. The animals rarely walked the whole 

 300 cm. without stopping or moving out of the beam. \\Tien- 

 ever this occurred they were gently picked up by the stumps 

 of the wings, returned to the beam, and placed behind the thread 

 which they had last passed. 



BEHAVIOR IN CONTINUOUS LIGHT OF DIFFERENT ILLUMINATIONS 



In experiment 1, 14 butterflies were tested. Each was al- 

 lowed to walk the whole distance of 300 cm. four times in suc- 

 cession, twice successively in direct sunhght and twice in sue- 



