424 ANNUAL KEPORT SMITHSONIAN INSTITUTION, 1938 



Such food-collecting worker bees we take for our experiment. 

 We use the scent of a little honey to attract some bees to our experi- 

 mental table, and feed them, for instance on a blue cardboard. 

 They suck up the food and, after homing, give it to other bees in 

 the hive. Then they return to the good feeding-place they have 

 discovered. We let them do so a while, and then we take away 

 the blue cardboard with honey and put a new clean blue cardboard 

 on the left, and a red one on the right of the feeding-place hitherto 

 existing. Should the boes remember that they found the food on 

 a blue cardboard, and should they be able to distinguish between 

 blue and red, they would fly to the blue color. That is exactly what 

 happens. 



This is an old experiment, already carried out by the English 

 naturalist John Lubbock. It proves that bees can distinguish colors. 

 But it does not prove that bees have color-sense. It is not the same 

 thing. There are (very rarely) totally color-blind men. They see all 

 things in much the same manner as we see them in an ordinary photo- 

 graph. They can distinguish between red and blue, for red is very 

 dark to them and blue much lighter. From our experiment we can- 

 not conclude whether the bees have distinguished red and blue by the 

 colors or by the shades, as a color-blind man does. 



For a color-blind human eye every color is a gray of a distinct degree 

 of brightness. What the brightness may bo for the eye of a color- 

 blind insect we do not know. We therefore make the following 

 arrangement. 



We place a blue cardboard on a table and beside it and around it 

 gray cardboards of all shades from white to black. On each card 

 there is a little watch-glass, but only the glass dish on the blue card- 

 board contains food (sugar water). In this way we train the bees to 

 the color blue. Bees have a very good memory for place. We there- 

 fore change the respective positions of the cards very often. But the 

 food is always placed on the blue cardboard, and the color therefore 

 indicates invariably where the food is to be found. 



After some hours or after some days we can make the decisive 

 experiment. The cardboards and glass dishes soiled by the bees are 

 taken away. We put on the table a new, clean series of differently 

 shaded gray cardboards, and anywhere between them we put a clean 

 blue cardboard with an empty glass dish. The bees remember the 

 blue color and alight only on the blue cardboard. They distinguish 

 it without hesitation from all degrees of gray. They therefore have 

 a color sense. 



Training to orange, yellow, green, violet, or purple gives the same 

 good results. But bees trained to scarlet red alight not only on the 

 red paper but in the same manner on black and all dark papers in our 

 arrangement. Red and dark are the same for bees' eyes. Bees are 



