FORMATION OF ASSOCIATIONS IN THE MAY-FLY 7 



Here again, at the beginning of each set of trials the stone 

 was placed at the greatest distance at which the specimen went 

 toward it on the preceding day, and then if necessary, it was 

 brought closer until the nymph made a straight trip toward 

 it, after which the distance was again gradually increased. 

 The number of inches in the first column shows the distance 

 at which the nymph made its first trip toward the stone each 

 day, and that in the second column indicates the distance at 

 which the trip was made at the end of 15 successful trials. 



The experiments demonstrate the learning capacity of H. 

 inter punctata. Not only did the insect show a tendency to 

 learn in an environment free from disturbing factors, but, as 

 can be seen from the results of the last experiments it learned 

 to do greater and greater distances toward a stone against the 

 rays of light. This is a fact of considerable interest, since these 

 nymphs have a decided negative phototaxis. But, on the other 

 hand they are very positive in their thigmotactic response, and 

 the results seem to indicate beyond doubt that the satisfaction 

 derived through attachment to the stone counteracted what- 

 ever reluctance the nymph may have experienced in going 



against the light. 



FEAR REACTIONS 



For this set of experiments I first took two large dishes and 

 placed six vigorous specimens in each. Those in one dish were 

 disturbed several times each day, while those in the other were 

 left unmolested. Although the insects always show a tendency 

 to gather into groups when placed in a dish of water, the ten- 

 dency is greatly diminished in a few days. Such was the case 

 in the undisturbed group. In the group undergoing disturbance 

 this tendency was greatly augmented, apparently through fear. 

 To overcome the grouping propensity the different individuals 

 were put in separate dishes with particles of food too small to 

 enable the insects to attach themselves, and to further obviate 

 the discomfort occasioned through the lack of proper thigmo- 

 tactic stimuli, the smooth glass bottoms of the dishes were 

 covered with sand. 



The room for this research was free from disturbance, and 

 before investigations for the procuring of detailed data were 

 attempted careful observations were made on the behavior of 

 a set of nymphs with a view to detecting and overcoming any 



