KELBER, A; BALKENIUS, A; WARRANT, E J; Lund University, Lund, Sweden; Lund University, Lund, Sweden; Lund University, Lund, Sweden: Colour Vision Abilities in Sphingid Moths

Humans are colour-blind at night, and this has been assumed to be true for all animals. However, colour vision is as useful for the detection and discrimination of objects at night as during the day. Sphingids have long been know to possess three spectral types of photoreceptors (sensitive to green, blue and ultraviolet light) and diurnal hummingbird hawkmoths Macroglossum stellatarum have been proven to use colour vision for flower discrimination. Using behavioural experiments, we have now demonstrated that even nocturnal hawkmoths including the species Deilephila elpenor use colour to discriminate flowers. They are able to do this under light levels equalling a dark moonless night, when humans are completely colour-blind. They are able to recognise flowers under changing colours of illumination, thus proving colour constancy. Under the lowest light level used in the experiments (0.0001 Cd/m²), the green receptors in one ommatidium that looks at the stimuli receive between 5 and 16 photons per integration time, and the blue and ultraviolet receptors receive even less photons. For colour vision to be possible with these low numbers of photons, we have to assume that temporal and/or spatial pooling take place in the moth eye. This is the first proof of an animal using colour vision for object detection under such dim light levels.