360 C. H. TURNER 



else walk rapidly about. These responses were not tropisms, for 

 the flights were pronouncedly random; there being no fixed 

 relation between the direction of the movement and the rays 

 of light. 



Frequently several seconds, and occasionally a few minutes, 

 would elapse between the impinging of the light rays and the 

 responses of the wasps, and individuals climbing upwards 

 through the sunlight, on reaching the upper edge of the bright 

 patch, often continued to walk about in the shadow for some- 

 time before coming to rest. In each of these cases the behavior 

 might be considered due to the fact that it requires time for 

 the stimulus to overcome the inertia of the nervous system ; but, 

 since, under exactly similar external conditions, the reaction 

 times are quite different, certain physiological conditions, of 

 which there were no external evidences, must influence the 

 behavior. Then too, occasionally wasps would be quite active, 

 for long stretches of time, when the external stimulus was a dim 

 light ; or else remain inactive, for equally long stretches of time, 

 when exposed to a strong white light. Wasps, when feeding, 

 frequently made no responses to a bright light. In this latter 

 case it is highly probable that the stimulus of the food had 

 a greater effect upon the hungry wasp than the light; but in 

 the other cases there was no external indication of the physio- 

 logical condition which caused the deviation from the usual 

 type of response. 



To ascertain if, in spite of the apparently random flights, 

 Trypoxylon albotarsus might not have an instinctive tendency 

 to move either towards or away from the light, at intervals, 

 the positions of the wasps were recorded. Some of these ex- 

 periments seemed to show conclusively a tendency to move 

 towards or settle in the light (Exp. 4) some seemed to demon- 

 strate an equally marked tendency to move towards or to settle 

 in the shadow (Exp. 5), some seemed to indicate no more ten- 

 dency one way than the other (Exp. 1). Sometimes, in the 

 same experiment, one portion would indicate that the wasps 

 had a strong tendency to move towards or to settle in the light 

 (Exp. 2; 10:30, 10:35) while other portions indicated an equally 

 strong inclination the other way (Exp. 2; 10:40, 10:45, 11:09, 

 11:15, 11:30). The only logical outcome of such a dilemma is 

 to conclude that the movements were purely random. That 



