THE VISION OF ARTHROPODS 



587 



later date, however, Carl von Hess (1913) concluded on the basis of 

 similar experiments that this insect moved towards different lights 

 depending on their relative intensity and that it was colonr-blind ; but 

 von Frisch (1914-50), in a long series of well-controlled experiments 

 wherein other factors were excluded, confirmed Lubbock's original con- 

 clusion and demonstrated that, after training, the bee reacted selectively 

 when presented with sugar-water associated with differently coloured 

 squares on a checkerboard, preferring blue and yellow to other hues. 

 These results were corroborated in the bee by Kiihn and Pohl (1921) 

 and Kiihn (1927), who used pure spectral colours, and by various tech- 

 niques in other species (Fig. 733). ^ 



The results of the earlier investigators gave the impression that 

 the bee was only able to distinguish between two groups of colours, 

 the yellow group and the blue-violet group ; but although this applies 

 in a general way to their reaction to the colours of flowers in nectar- 

 hunting, it was later demonstrated that this insect was able to dis- 

 tinguish several colours within each group if trained to show differential 

 responses (Lotmar, 1933). Thus after training to bands of spectral light, 

 bees have been found to distinguish four regions : 650-500 m^u, (red- 

 green), 500-480 mfx (green-blue), 480-400 m/x (blue-violet), and 400-310 

 mjjt, (ultra-violet), the last being probably perceived as a colour 

 (Kiihn, 1927 ; Hertz, 1939). At a later date Daumer (1956) interpreted 

 the reactions of bees as mediated through 3 types of receptors — yellow, 

 blue, and ultra-violet. Red flowers seem to be distinguished because 

 of their reflection of ultra-violet. The colour system of the bee is 

 therefore widely different from that of man.- Moreover, on testing 

 optomotor reactions, von Buddenbrock and Moller-Racke (1952) 

 concluded that butterflies have three receptors — an orange-red, a 

 yellow and a green-blue. It would thus ajDpear that different species 

 have different types of colour vision (Use, 1928-49 ; Schlegtendal, 

 1934), while some may be colour-blind.^ Finally, various regions of 

 the compound eye may react differently : thus the antero -ventral 

 jDortion of the eye of the water-boatman. Notoiiecia, is equally sensitive 

 to all colours while the dorso-posterior part shows preferential differ- 

 ences in colour-sensitivity (Liidtke, 1938-54 ; Rokohl, 1942 ; Resch, 

 1954). 



It is interesting that different mechanisms are apphed in different activities 

 since innate reactions show a selective responsiveness to very different stimuli ; 

 one reaction inay be released by the intensity of light, another by its wave- 



^ The bee-fly, Bombylius, and the hawk-moth, Macroglossa — Knoll (1925-26) ; 

 butterflies, Pieris,Go)iepteri/.v and Vanessa — Use (1928). Tinbergen et al. (1942); the aphid, 

 Myzus — ]Moricke (1950) ; the fruit-fly, Drosophila — Fingerman and Brown (1952-53). 



^ And also different from that of birds which are attracted preferentially to red 

 flowers (p. 630). 



^ Such as the nocturnal stick-insect, Dixippus, and the bug, Troilus (Hundertmark, 

 1936-37; Schlegtendal, 1934). 



Xotonecta 



