782 



LIGHT AND LIFE 



^6°\ 





Fig. 3. Tentative chroraaticity diagram for the honeybee based on the work 

 of Daumer (9). The behavioral experiments of Daiimer lead to the prediction 

 that any color can be matched for bees by an appropriate mixture of three mono- 

 chromatic reference stimuli, e.g., ultraviolet (360 m^), blue-violet (440 mfi), and 

 yellow (588 m/x). Any light, therefore, can be represented in Fig. 3 by a point; 

 for example, "W" is the white of the xenon emission spectrum. The proportions, 

 in fractions of the total energy — the chromaticity coordinates — of the yellow and 

 blue reference stimuli required for a colorimetric match of the light represented 

 by the point are given by the coordinates of the point, 588 m^oi on the abscissa 

 and 440 m^ on the ordinate. Since the sum of the three chromaticity coordinates 

 is 1, the fraction of the energy at 360 mfj. can be calculated by difference. The 

 locus of tlie spectrum is given by the experimental points; however, as is sug- 

 gested by the dashed line, it may actually lie somewhat outside the triangle, for 

 it is questionable whether this kind of experiment is sufficiently precise to reveal 

 the necessity for small negative \alues of one of the chromaticity coordinates. The 

 complementary to 360 m/i, is 490 niju, for both wavelengths lie on a straight line 

 passing through the white point. Similarly, the point "P" is the "bee-purple" 

 complementary to 440 m^it and is composed of 79 per cent 588 m/M and 21 per 

 cent 360 nifi. 



responses to blue-green light occur when excitation is confined (or 

 nearly so) to the niitldle and long wavelength receptors. A similar 

 narrow region oi the spcctrinn possessing distinct color for bees and 

 exciting both the idtraviolet and blue-violet receptors might well 

 exist somewhere between 440 and 875 m^t, but this is a region of the 

 spectrum which has not been as adetjuately explored. 



These behavioral experiments imply the presence of receptors maxi- 

 mally sensitive in the near ultraviolet, blue, and green-yellow regions 



