Sensory Discrimination: Vision 155 



of color proper rather than brightness was forthcoming 

 (267). Similar observations were made by Lubbock on 

 ants, which in their underground life are negatively pho- 

 totropic, the eggs and larvae apparently needing darkness 

 in order to develop, but on their foraging expeditions are 

 comparatively indifferent to light. They showed a pref- 

 erence for red when tested, and a tendency to avoid the 

 ultra-violet rays, so marked that they preferred bright day- 

 light from which these rays had been extracted by chemi- 

 cal screens, to darkness that contained the ultra-violet 

 rays (441, pp. 207 ff.). Graber suggested that the ultra- 

 violet rays produce a skin sensation in the ants; but 

 Forel agrees with Lubbock that the effect is visual, because 

 he found that varnishing the eyes made the ants indiffer- 

 ent to ultra-violet (231). Ants of the family Lasius seem 

 to be normally insensitive to these rays (235). It is just 

 possible, then, that a visual sensation of quality wholly 

 foreign to our experience may accompany the action of 

 ultra-violet rays on insects. Loeb has noted that the 

 relative effect of violet and ultra-violet vibrations, as 

 compared with that of the rest of the spectrum, is greater, 

 the less developed the visual organ (419). Termites, which 

 seek darkness, prefer red to blue colored glass (6). 



Lubbock's experiments on the color sense of bees are 

 more to the point than those on ants, for they were made 

 not by the Preference Method, but by associating a color 

 with food. No precaution, however, was taken against 

 the brightness error. He found that bees which had eaten 

 honey from blue paper would pick out the blue pieces from 

 a number of differently colored papers, whose positions 

 were altered during the experiments (441). Forel got 

 similar results, and reports that a bumblebee thus trained 

 selected all the blue objects in the room for special ex- 



