484 R. T. YOUNG 



to more closely resemble its surroundings), and one on charred wood, 

 the latter combination showing the greater contrast. Before I had 

 left the cage after placing the insects, the grackle crossed from the 

 opposite end of the cage to the backgrounds and took the insect from 

 the charred wood, leaving that on the grass and straw untouched. 

 This was left in position and a few minutes later it too was taken. 

 Comparing Experiment 25 above with Experiment 27, one is impressed 

 with the influence which the attention of the bird exercised on th^ 

 rapidity with which the results were obtained. In the former experi- 

 ment, the insects were apparently unseen for over fift}^ minutes, al- 

 though during this time the bird several times came near them; while 

 in the latter they were taken immediately, due in all probability, to 

 the fact that the bird realized that food was being prepared for it on 

 the backgrounds. Why its attention was attracted more readily in 

 one experiment than in another is uncertain. I shall refer to this 

 question later (p. 493). 



Experiment 28. Figures 27 and 61. One moth (Noctuid sp.) was 

 placed on brown leaves and bits of bark and one on charred wood 

 within about 7 cm. of each other. The former moth closely resembled 

 its background, while the latter combination presented a good contrast. 

 In three minutes the grackle dropped from its perch to the ground and 

 walked directly to the backgrounds, passing by the moth on the leaves. 

 It then paused for a few seconds to inspect the moths, before seiz- 

 ing that on the charred wood, immediately followed by that on the 

 leaves. 



Experiment 29. Figures 26 and 27. Same as Experiment 28, 

 except that a background of straw was substituted for the leaves and 

 bark, the moth-wood combination presenting the greater contrast. 

 The grackle immediately dropped to the ground and walked directly 

 towards the backgrounds, but its attention being apparently diverted 

 by some object outside of the cage, it ran past, returning on the side 

 of the straw, from which it seized the moth, and then that on the wood. 



Experiment 30. Figures 27 and 59. One moth (Noctuid sp.) was 

 placed on charred wood and one in an angle of a dead leaf so that the 

 wings overlay it, with the head and thorax projecting over the ground, 

 thereby reducing the relief and enhancing the resemblance of the insect 

 to its background The insects were placed 6 or 7 cm. apart. In ten 

 minutes the grackle dropped to the ground and approached the back- 

 grounds on the side of the latter moth, but passed it by and seized the 

 former, then turning, it apparently was about to seize the latter when 

 I interfered. 



Experiment 31. Figures 27 and 40. One Gryllus was placed on 

 charred wood mixed with a little earth, and one on ashes. The former 

 combination presented to my eye a close resemblance. The grackle 

 was about 1.6 m. distant during the arrangement of the experiment. 

 As I was leaving the cage it went directly to the backgrounds and 

 approaching the charred wood first, seized the insect upon it, immedi- 

 ately followed by that on the ashes. 



