Behavioural analysis of chromatic and achromatic vision in the ant Formica cunicularia (Hymenoptera: Formicidae).

Responses of Formica cunicularia foragers to monochromatic light stimuli of 370, 440, 540, 590 and 640 nm were evaluated in different experimental conditions using a Y-maze apparatus and a circular orientation platform. The results showed that foragers responded significantly to all test wavelengths at certain intensities but could only discriminate 370 and 540 nm from alternatives irrespective of intensity changes. Furthermore, they were also capable of discriminating two long wavelengths, 590 and 640 nm, using a photon catch mechanism by their green photoreceptors. Foragers also discriminated stimuli pairs of same wavelengths based only on intensity differences they provide. The overall results show that F. cunicularia foragers have a dichromatic colour vision system based on inputs of two possible photoreceptor types sensitive to UV and green. The results also yielded evidence showing that their visual systems provided foragers a sensitivity also for wavelengths corresponding to blue and red ranges of the spectrum.