Holmes, TJie Reactions of Ranatra to Light. 331 



\y exposed. It may even follow the light by turning towards 

 the blind side as the following experiment shows : 



The right eye and all but a small part of the posterior surface of the left was 

 thickly blackened over. When the specimen came out of its death feint it walked 

 nearly straight to the light. The light was then moved over toward the right 

 side of its path several times, and the course of the insect was changed so as to 

 continue going towards it. The light was then held to the right and behind the 

 body and the insect circled around to the right. By keeping the light in the 

 proper position the insect could be caused to keep circling around to the right in 

 the same spot. The head and body in these movements were tilted over slightly 

 to the right, but not so strongly as they are inclined to the left when the light is held 

 on that side. The insect would perform circus movements to the left more 

 readily than in the opposite direction, but it would make sharp turns to the right 

 whenever it was necessary to maintain a position of orientation. When the light 

 was placed behind the body the insect would usually turn around to the left to 

 reach it. If, however, it was placed behind the body and a little to the right the 

 specimen would turn around towards the right side. 



12. Reactio7is of Specimens with only Smallli Part of the 

 Lateral Surface of One Eye Exposed. The right eye of a speci- 

 men was completely blackened over and all but a small part of 

 the lateral surface of the left. 



The insect was at first sluggish. When the light was held on the left side the 

 head and body were tilted over towards it, and the specimen turned slowly to the 

 left. When the light was placed two feet ahead of the specimen it moved very 

 slowly and with the greatest hesitation, turning this way and that as if seeking to 

 get its bearings, but going, nevertheless, nearly straight to the light. Although 

 a decided tendency to make circus movements to the left was manifest, deviations 

 in that direction were corrected by a direct turn towards the right side. When 

 the light was held on the right side of the body the insect seemed confused and 

 undecided which way to turn. When the light was held to the front and to the 

 right so that the rays struck the body at an angle of about 45° the insect 

 would not turn towards the light but moved about aimlessly until the left eye 

 was presented to the light when it would turn to the left and go up to it. By 

 keeping the light nearly in front of the body the insect would follow it all around 

 the table. The experiment was then tried of holding the light farther over 

 towards the right. The insect could then be caused to keep turning slightly 

 towards the right in order to follow it. When the light was held still further to 

 the right the insect still followed it. After a while it would follow it when held 

 in a position to which it would not turn at the beginning of the experiment. 

 After having got into the way of turning to the right side it would turn in that 

 direction much more abruptly than at first. 



A second specimen was treated in the same way, but it showed at first a pro- 

 nounced negative reaction. It would pay little attention to the light except 

 when it was held opposite the left eye when the insect would move away from it 

 sidewise, much like a crab, by extending the legs on the left side and flexing 



