THE BEHAVIOR OF COCKROACHES 83 



diately turned towards the darker part, which it entered. There- 

 upon I turned the current upon it. The animal, on receiving 

 the electric shock, ran wildly about, tried to crawl up the walls, 

 and then ran back to the light part. As soon as it had retreated 

 to the lighter region, I switched off the circuit. After a short 

 time, the cockroach again entered the darkened part and re- 

 ceived another shock. When this procedure had been repeated 

 a variable number of times, according to individual differences, 

 the animal running in the direction from light to dark, on 

 attaining the boundary line between the light and the dark, 

 would suddenly stop, move its head and thorax in all directions 

 and begin rapidly working with its antennae. After a time 

 it usually turned back to the light. This behavior is, I think, 

 the first stage in the overcoming of phototropism by training; 

 untrained cockroaches do not behave in this manner. After 

 a short time the animal would again return to the darkness, 

 and again receive a shock. Its behavior now completely changed, 

 for it no longer ran about in the dark region, but at once 

 retreated towards the light. Having attained the boundary 

 line between light and darkness, it turned towards the light. 

 The number of turnings back from the boundary line between 

 darkness and light into the light without receiving a shock 

 increased with training. I considered the training complete 

 when the animal, being in the light, turned back to the light 

 ten times on arriving at the boundary line between light and 

 darkness, without receiving a shock. All of the ten cockroaches 

 used in my experiments succeeded in doing this. 



During the experiments, when experience of the situation 

 had already been gained, it repeatedly happened that an animal 

 coming from the light to the boundary line between light and 

 darkness, remained still of its own accord, with its head pointed 

 towards the darkness. When I excited the animal to move by 

 stroking its back (dorsum) by means of a strip of paper, it strug- 

 gled against going into the darkness and turned towards the 

 light in order to escape the irritating strip of paper. Table I 

 shows the results of the experiments. 



With the exception of Nos. 3 and 5, the cockroaches were 

 tested at the same time of day, two o'clock in the afternoon, 

 without intermission until they finally made the required num- 

 ber of turnings back. The time necessary for training was on 



