BEHAVIOR OF THE COMMON ROACH. 353 



consumes from fifteen to sixty minutes. The next few trials the 

 roach behaves in practically the same manner, hut makes fewer 

 and fewer mistakes. Finally, after a prolonged series of trials, 

 in spite of frequent lapses, the mistakes are gradually eliminated 

 and the roach runs the maze, without making any errors, in 

 from one to four minutes. As the roach moves along, the anten- 

 nae are waving almost incessantly, as though seeking stimuli. 

 The mistakes are eliminated so gradually that this may be con- 

 sidered a trial and error type of learning, if one may use that 

 expression without predicating the absence of sensations and 

 feelings. Such, in brief, is the behavior of the common roach 

 on the maze; but one is impressed by the variations displayed. 



These variations in behavior are of tw r o types: differences due 

 to age and modifications due to individuality. The older 

 roaches usually move much more slowly and much more carefully 

 than the younger ones. Roaches from ten to twelve millimeters 

 long usually move so rapidly that they might well be called frisky. 

 The slower gait of the older roaches is not due to feebleness, for 

 they are fleet enough when placed on the floor of a room; but 

 to what, in human beings, W T C call caution. As a result of this 

 difference in speed, the younger roaches, on their initial trial, 

 usually run the maze much more quickly than the adults; but, 

 in doing so, make many more mistakes. 



The variations due to individuality are the ones that are 

 especially impressive. Some roaches, with humped backs, move 

 sedately along in the middle of the runways, pausing at each 

 corner to explore upward, outward and downward with their 

 antennae: others trot along in the middle of the runways, at 

 first usually falling into the water at each angle, but later slowing 

 up at the corners, exploring with their antennae and moving 

 onward. Some roaches, with their bodies extended until they 

 are practically flat, drag themselves along so slowly that it taxes 

 the patience of anyone who happens to be watching them; 

 others, moving sometimes slowly and sometimes rapidly, always 

 keep the claws of the legs of one side of the body in contact with 

 the edge of the runway. When such a roach turns a corner it 

 usually, although not invariably, crosses to the opposite side of 

 the runway and clings to the edge with the legs of the corre- 



