Holmes, The Reactions of Ranatra to Light. 321 



features of interest is shown in the following experiments per- 

 formed upon one individual : 



The specimen was taken out of water from a darkened room where it had 

 been placed the day before and placed near a light on a table. Soon it awoke 

 and began to turn away from the light. The light was moved around it in differ- 

 ent directions and, although the insect seemed at first dazed and walked about 

 with no very decided tendency to go either towards or away from the light, it 

 soon began to show a more pronounced negative reaction. It was then picked 

 up by the breathing tube and placed at right angles to the rays from an incandes- 

 cent lamp four feet away. During eight successive trials in which the right and 

 left sides were presented alternately to the light to eliminate any tendency to turn 

 to a particular side that might be due to habit, it turned in each case away from 

 the light. Its movements were at first slow and stealthy. At the ninth trial it 

 turned slightly towards the light, but reached the edge of the table before it had 

 turned very far. At the tenth and several subsequent trials it turned towa»ds 

 the light and went up to it rather quickly. Its movements now became much 

 more rapid. It was then placed ten feet from the light and still showed a posi- 

 tive response. It was then placed on the floor 22 feet away from the light, which 

 was laid on the floor at the other end of the room. Although the light to which 

 it was exposed was relatively very dim, the insect traveled to the light across the 

 whole length of the room in nearly a straight line. When brought near the light 

 the insect became more and more strongly phototactic and in about twenty min- 

 utes its eff^orts to reach the light became almost frantic. After a time it became 

 apparently exhausted and settled down to rest. 



It was then immersed in water and laid down on the table. Its movements 

 were very sluggish and its responses to light slow. When placed at right angles 

 to the rays it would slowly and stealthily creep away. It did this eight times in 

 succession when the right and left sides were alternately placed towards the light. 

 At the ninth and several subsequent trials it went towards the light. Then it 

 was caused to follow the light about for a few minutes and soon it became quite 

 excited. It was picked up and stroked but it could not be induced to feign 

 death and as soon as released it made for the light, which was four feet away. 

 It was then held in water for several seconds, but as soon as liberated it showed 

 an unmistakable though not very strong positive reaction. It went up to the 

 light, touched the bulb with its anterior legs, jerked back quickly as if burned, 

 then stopped for a moment and walked away from the light. As the light was 

 moved about, the insect would flee from it repeatedly as if it feared a repetition 

 of its disagreeable experience. Soon, however, its responses became weak and 

 indefinite ; its movements were sluggish. After a time it showed a positive reac- 

 tion and began to follow the light all around the table. A little later it became 

 much excited and flew towards the light repeatedly. The light was placed in a 

 cylinder of water and the insect struggled to go towards it for ten minutes. It 

 was then held in cool water for a short time and placed again on the table. 

 After this experience it showed a marked negative response. The light was 

 moved about the insect in various directions so as to keep it close to the body for 

 about twenty minutes when positive phototaxis was again induced. When its 

 reaction became very strong, the insect was picked up and stroked, but it feigned 



