Flower Cues for Hawkmoths: Colour, Place and Odour

Sammanfattning: Flowers use different cues to attract pollinators including colour and odour. How do hawkmoths use these cues to find the flowers? This question was investigated in two species of hawkmoth, the diurnal species, Macroglossum stellatarum, and the nocturnal species, Deilephila elpenor. Both species have colour vision and D. elpenor can discriminate colours under very dim light intensities. Both species of moth also have colour constancy, which allows them to identify colours under changing illuminations. The hawkmoths can not only recognise colours under changed illumination, they can also use the colour of the illuminating light as a context stimulus. When there are many flowers with similar colours, it may be difficult to identify a specific flower by its colour. In this situation, D. elpenor learns the place of the rewarded flower instead of its colour. When the flowers have dissimilar colours, the moth continues to use colour as a cue. Place learning appears to be a short-term effect since the moth returns to selecting according to colour the day after. Both species can detect flower odours. D. elpenor relies on odour more than on colour, while M. stellatarum spontaneously forages from odourless flowers. It requires learning to select a flower based on odour. The ability of the diurnal moth to use odour depends on the colour of the flowers. With a more preferred colour, they are less likely to learn the odour. The results of the experiments all points towards the conclusion that moths do not only use one sensory modality to find flowers ? they use all modalities available to them.