4 6 



C. H. TURNER. 



It is probably unwise to draw conclusions from only a hundred 

 experiments; but, these experiments suggest that the water does 

 have a directive influence upon this giant water bug. 



A SCAVENGER BEETLE (Tropisternus) (PLATE V). 



In experimenting with the checkerboard plate nineteen in- 

 dividuals of this species were induced to perform 571 experiments. 

 In most cases the board was ten to twenty feet from the water. 

 In one case it was fifty feet (number 18); in another case it was 

 100 feet (number 19). The results of the experiments are recorded 

 in Table VI. 



TABLE VI. 



A SCAVENGER BEETLE (Tropisternus) ADULTS. 



In an infinite series of experiments, if the factors considered 

 did not influence the movements, 25 per cent, should have been 

 toward the water, 12.5 per cent, toward the sun and 12.5 per 

 cent, toward the direction the head originally pointed. The 



