EXPERIMENTS ON PROTECTIVE COLORATION 471 



uppermost. Two backgrounds were employed, one of dry earth mixed 

 with lime and dead leaves, the other of moist earth. The contrast 

 between the mouse and the latter background was much stronger than 

 that between the mouse and the former background. In ten minutes 

 one hawk left its perch alighting near the mice but apparently not see- 

 ing them till after alighting. It alighted with its head turned away 

 from the background of moist earth and facing the mixed background. 

 After alighting it seized the mouse on the latter. 



Exjieriment 12. Figures 1 and Uf. The same prey and backgrounds 

 were employed in this as in the last experiment, but the mouse on moist 

 earth was placed venter uppermost, while that on mixed lime, leaves, 

 and earth, was placed dorsum uppermost, the former presenting the 

 more striking contrast. In six minutes a hawk left the perch and fly- 

 ing directly to the mice seized the one on the moist earth. 



Experiment 13. The arrangement of backgrounds and prey em- 

 ployed in this experiment was precisely the same as in the last, except 

 that the position of the backgrounds was reversed. For eighteen 

 minutes the hawks remained on the perch, during which time one hawk 

 looked down several times and appeared undecided whether to fly 

 down or not. It finally flew directly to the backgrounds and took the 

 mouse from the moist earth. 



Experiment 14-- Figures 1 and 8. In this experiment one back- 

 ground of lime and one of mixed lime, earth, and leaves was employed 

 one Mus being placed on each. After about seventeen minutes, dur- 

 ing which time the hawks remained on their perch, one of them cir- 

 cled over the mice and returning lit near the perch. It remained here 

 for a few minutes with its back turned toward the mice, while a second 

 hawk in about three minutes flew directly to the mouse on the lime, 

 which it seized. 



Experiment 15. Figures 2 and 13. One light colored Mus and one 

 Blarina were placed on moist earth. After thirteen minutes a hawk left 

 the perch and flew to the ground near the prey, and then returned to 

 the perch. Six minutes later a hawk flew to the background and lit 

 with its side toward the shrew. After alighting (apparently not before) it 

 saw the mouse, which it seized, and then took the shrew. In this ex- 

 periment the greater contrast with the background was presented by 

 the mouse. 



Experiment 16. Figures 6 and 11. One background of lime and 

 one of mixed earth, lime, and dry leaves were arranged in this experi- 

 ment, and on each was placed a Microtus. Three minutes after the 

 mice were placed a hawk left its perch and flew to a point between 

 the backgrounds and close to each. It then retreated a few steps, 

 returned and seized the mouse on the mixed background. 



Experiment 17 . Figures 1 and 8. The same backgrounds were em- 

 ployed in this experiment as in the last, two Mus being used as prey. 

 In three minutes a hawk left its perch and flying to the ground took 

 the mouse from the mixed background. 



