Simultaneous color contrast in the honeybee

Summary

Simultaneous color contrast was investigated with a behavioral training technique. Single bees were trained to land on one of 9 differently colored test fields on a grey surround and were tested with the same test fields on blue and yellow surrounds.

Color contrast was inferred from a change of choice behavior: Bees trained on a “bee-subjective” blue-green test field with the grey surround preferred with the blue surround a test field which was more blue, and with the yellow surround a test field which was more green than the training test field (Fig. 3). These choices indicate that the blue surround changed the hues of the test fields towards green (yellow) and the yellow surround towards blue-violet. Direction and strength of the color contrast is shown in the color triangle of the bee (Fig. 4).

The same blue and yellow surrounds also lowered the bee's sensitivities for monochromatic lights of 431 and 535 nm, respectively, which stimulate the blue and green receptors maximally. A selective desensitization of these receptors can qualitatively explain the effect of color contrast (Figs. 5 and 6).

Small annular surrounds of 5–10 mm width presented on a black background produced approximately the same color contrast effect as large surrounds of 50 cm diameter (Figs. 7 and 8). On medium-grey and light-grey backgrounds the same surround widths elicited weaker contrast effects (Fig. 8).

Spatial separations between test field and surround by black borders greatly reduced the color contrast effect when the surround was small (Fig. 10). With large surrounds, however, the strength of color contrast was only slightly diminished (Fig. 9).

On test fields of different diameters color contrast effects of varying strengths were observed (Fig. 11).