Innate preferences for flower features in the hawkmoth Macroglossum stellatarum

The diurnal hawkmoth Macroglossum stellatarum is known to feed from a variety of flower species of almost all colours, forms and sizes. A newly eclosed imago, however, has to find its first flower by means of an innate flower template. This study investigates which visual flower features are represented in this template and their relative importance. Newly eclosed imagines were tested for their innate preferences, using artificial flowers made out of coloured paper or projected onto a screen through interference filters. The moths were found to have a strong preference for 440 nm and a weaker preference for 540 nm. The attractiveness of a colour increases with light intensity. The background colour, as well as the spectral composition of the ambient illumination, influences the choice behaviour. Blue paper disks against a yellowish background are chosen much more often than the same disks against a bluish background. Similarly, under ultraviolet-rich illumination, the preference for 540 nm is much more pronounced than under yellowish illumination. Disks of approximately 32 mm in diameter are preferred to smaller and larger ones, and a sectored pattern is more attractive than a ring pattern. Pattern preferences are less pronounced with coloured than with black-and-white patterns. Tests using combinations of two parameters reveal that size is more important than colour and that colour is more important than pattern.