5 i <> ANTS. 



for it is certain that prolonged exposure causes many ants to become 

 indifferent to light, and 1 know two species (Hypoclinea inaruc and 

 t/itt/atcs ) which seem to be normally in this condition. 



That the eyes of our common ants are sufficiently developed to enable 

 their possessors to discriminate colors and forms has been maintained 

 by several observers. Lubbock (1882), Forel ( i886-'88, 1 900-0 1), 

 Forel and Dufour (1902) and Miss Fickle (1902) have made many 

 experiments to test the ants' power of discriminating light of different 

 wave lengths. Lubbock found that ants avoid the ultra-violet rays of 

 the spectrum, and Forel, by hoodwinking ants, showed that these rays 

 were perceived through the eyes and not through the general integu- 

 ment as Graber (i883~'85) had maintained. Miss Fielde summarizes 

 her results, which agree with those of Lubbock and Forel, in the fol- 

 lowing words : " The ants manifested no liking for any of the rays of 

 light. If obliged to stay in light rays of some sort, the rays of longer 

 wave-lengths are preferred to those of shorter wave-lengths. Dividing 

 the spectrum, as we know it, into red, green and violet, we may 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 violet. In this regard the 

 eyes of the ant appear to be the reverse of our own. Our eyes per- 

 ceive in the spectrum three fundamental colors red, green and violet. 

 The eyes of the ant perceive there only two fundamental colors one 

 made up of the red and green rays, the other of the violet and ultra- 

 violet rays." She says further : " 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 deter- 

 mined by the wave-length in the light-ray, and since the ants dis- 

 criminate between rays of different wave-lengths, they probably per- 

 ceive color in the rays. Sensitivity to the length of the wave indicates 

 perception of color." 



Forel and Dufour also experimented on ants with Roentgen r^ys. 

 These were directed up through the bottom of an artificial nest, and 

 although they were allowed to act on the ants and their brood for fifteen 

 minutes, the insects made no response. Moreover, a week later, they 

 showed no signs of having sustained any injury from the experiment. 



If we accept Exner's view that the compound eye of insects forms 

 of an object a single upright image, which is the more definite the 



