1902.] NATURAL SCIENCES OF PHILADELPHIA. 623 



are preferred to those of shorter wave-length. Dividing the 

 spectrum, as we know it, into red, green and violet, we might say 

 that to the ants' eyes red and green are most like the darkness 

 that they prefer, and that violet is to them most luminous; or that 

 the red and green are less visible to them than is the violet. In this 

 regard the eyes of the ant appear to be the reverse of our own. 



Our eyes perceive in the spectrum three fundamental colors — red, 

 green and violet. The eyes of the ant may perceive there only 

 two fundamental colors— one made up of the red and green rays, 

 the other of the violet and ultra-violet rays. 



After the experiments above recorded were completed, I put five 

 queens and about three hundred workers, from a colony freshly 

 brought from its natural nest, into each of five similar artificial 

 nests, having opaque floors and walls and colorless glass roofs. 

 The first nest I covered Avith cardboard, making its interior dark. 

 The second I covered with panes transmitting only red and green 

 rays, and in this the ants disposed themselves through the compart- 

 ments in about the same way as did those in the first, the dark, 

 nest. Over the third I put panes transmitting yellow, green, blue 

 and indigo rays, and in this the ants disposed themselves with 

 considerable regard to the shade afforded by the sides and partitions 

 of the nest. Over the fourth I put panes transmitting only the 

 rays at the violet end of the spectrum, and in this nest the ants 

 disposed themselves with the same manifest effort to avoid the light 

 as they did in the fifth nest, which was covered with colorless glass. 

 Interchanging the panes caused the ants to rearrange themselves 

 in accordance with the above scheme of relationship to the light. 



Bearing in mind the fact that the ants showed no preference for 

 red alone over the red and green (Experiment 3), it appears that 

 the eye of the ant is not well adapted to the reception of light -rays 

 whose wave-length is longer than in the violet rays ; that it receives 

 blue and indigo more perfectly than red, orange, yellow and 

 green ; and that there is a sudden increase of luminosity in the 

 light-rays at that point in the spectrum where violet begins for our 



eyes. 



The ants may discern colors, and yet have no preferences among 

 the colors discerned. Color is determined by the wave-length in 

 the light-ray, and since the ants discriminate between rays of 

 different wave-lengths, they probably perceive color in the rays. 



