2 J. E. WODSEDALEK 



formation of associations in lower insects has hitherto been the 

 subject of very few experimental investigations. 



REACTIONS TO OBJECTS 



Different nymphs vary greatly in their response to objects 

 under similar conditions. Some, for instance, will go as far 

 as 1 1 inches in a direct line toward a stone about one cubic 

 inch in size, while others seem to be unaware of the object even 

 when it is much nearer. 



I experimented with 20 specimens in a large glass basin, 

 evenly lighted and evenly colored. The nymphs were placed, 



Figure 2. Diagram of apparatus used in the experiments 

 on reactions to objects 



one at a time, in a small glass passage, represented by AB in 

 the diagram, within and close to one side of the large basin, 

 and a stone a little more than one cubic inch in size was placed 

 about a foot away from the opening of the glass tunnel. 



The little glass tunnel was to prevent random movements. 

 Specimens dropped into water, owing to excitement, are apt 

 to swim about in any direction. A specimen would be care- 

 fully placed at the closed end of the passage, which was suffi- 

 ciently wide to enable it to move freely forward, but which 

 would not permit it to turn around. Slight stimulation from 

 behind induced it to swim forward. In doing so it had ample 

 time to get a view of the enclosure before it reached the open 



