C. H. TURNER. 



TABLE VIII. 



THE WHIRLIGIG BEETLE (Gyrinus sp.?) (PLATE VII). 



In working with the checkerboard plate twenty-one individ- 

 uals were used. With the board from ten to fifteen feet from 

 the water, 551 experiments were performed. The results are 

 recorded in Table IX. 



In an infinite series of experiments, if the factors considered 

 have no effect of the movements of the creatures, then 25 per 

 cent, of the movements should have been toward water; 12.5 

 per cent., toward the sun; 12.5 per cent, toward the original 

 position of the head. These experiments yielded 52.6 per cent, 

 of movements toward the water, 6.7 per cent, toward the posi- 

 tion of the sun and 22 per cent, toward the original position of 

 the head. In one individual the per cent, of movements toward 

 the water was 95, in four cases it was between 80 and 90, in 

 three cases it was between 60 and 70, in four cases it was between 

 50 and 60, in five it was between 40 and 50. In the case of only 

 three individuals was the per cent, of movements toward water 

 less than 30. Evidently, the whirligig beetle, when moving on 

 the checkerboard plate, is largely directed by the nearest body of 

 water. They act as though they were positively hydrotropic. 



In addition to the work upon the checkerboard plate, tin- 

 following experiments were conducted in the open. Twelve 

 specimens were placed in a dry tray ten feet from the water. In 

 less than half an hour all had flown to the water. Ten spin inu-ns 

 were placed in a dry tray twenty feet from the water. In less 

 than half an hour all had flown to the water. Ten specimens 



