1902.] NATURAL SCIENCES OF PHILADELPHIA. 625 



The withdrawal of the ants from the violet rays may have 

 psychological relation to rain, or to some form of water. Four 

 times when I put ants into cells of which one-half was covered with 

 blue glass, the ants caught up their inert young and piled it all 

 on top of the food enclosed in the cell, as if to raise the young out 

 of the wet. This action on their part was so extraordinary as 

 to cause me to make record of it. The ants living in my other 

 Petri cells during the past two years have always assembled the 

 young on the side of the cell opposite the food, and have in no 

 case laid live larvae or pupae on the food-pile. 



The plasticity of the ants is remarkably shown in their gradu- 

 ally learning to stay where they were never disturbed by me, under 

 ravs from which their instincts at first withdrew them. 



40 



