Detection of coloured patterns by honeybees through chromatic and achromatic cues

We asked whether the detection range of two-coloured centre-surround patter ns differs from that of single-coloured targets. Honeybees Apis mellifera w ere trained to distinguish between the presence and absence of a single-col oured disc or a coloured pattern at different visual angles. The patterns p resented colours which were either different in chromatic and L-receptor co ntrasts to the background, equal in chromatic but different in L-receptor c ontrasts, or vice-versa. Patterns with colours presenting only chromatic co ntrast were also tested. Patterns with higher L-receptor contrast in its ou ter than in its inner element were better detected than patterns with a rev ersed L-contrast distribution. However, both were detected worse than singl e-coloured discs of the respective colours. When the L-receptor contrast wa s the same for both elements, the detection range of the two-coloured and s ingle-coloured targets was the same. Patterns whose colours lacked L-recept or contrast were detected just as single-coloured targets of the same colou rs. These results demonstrate that both chromatic and L-receptor contrasts mediate the detection of coloured patterns and that particular distribution s of L-receptor contrast within a target are better detected than others. T his finding is consistent with the intervention of neurons with centre-surr ound receptive fields in the detection of coloured patterns.