FORMATION OF ASSOCIATIONS IN THE MAY-FLY 5 



records in going toward a stone in an evenly lighted environ- 

 ment were taken and with each 21 daily experiments were per- 

 formed. At the beginning of each set of trials the stone was 

 placed at the greatest distance at which the nymphs went 

 toward it on the preceding day. Usually, the stone had to 

 be brought somewhat closer than this before the nymph made 

 its first trip toward it. Then the stone was taken farther away 

 after each successful trip, until a distance was reached when 

 the nymph seemed to pay no attention to the object. This 

 necessarily had to occur during each set of trials in order to 

 ascertain the greatest distance at which the nymphs would go 

 to the stone. An over-rating of the distance necessitated the 

 bringing back of the stone to a place where another successful 

 trip was made. The distance made each day on the twelfth 

 successful trip was recorded. The results of this test of the 

 learning ability of three individuals are given in table III. 

 The number of inches indicate the distance each nymph would 

 go toward the stone at the end of 12 successful trials. It will 

 be noticed that two of the specimens increased their distance 

 slowly but steadily, while one varied in its daily behavior and 

 even at the end of three weeks apparently had learned nothing. 



TABLE III 

 Showing the Learning Capacity of Three H. Inter punctata Nymphs 



