Colour Discrimination Functions of the Humming Bird Hawkmoth (Macroglosum Stellatarum) Modelled From Behavioural Choices

The hummingbird hawkmoth ( Macroglossum stellatarum) is a diurnal, visually oriented insect that has become an important animal model for comparative studies. Hawkmoths use colour information to find and identify profitable flowers, and they are major pollinators in various regions of the world. Recent research on other flower visiting animals including bees, hoverflies and birds shows that their respective colour choices for target-distractor stimuli of varying similarity can be reliably modelled using sigmoidal-type continuous functions, as postulated by von Helversen 50 years ago. We formally test if colour choices by M. stellatarum can also be reliably explained by these sigmoidal functions that are important for modelling plant-pollinator interactions in other animals. We fit multiple formulations of sigmoidal functions selecting those which best fit the observed data. We show that colour vision in hawkmoths varies across various regions of colour space. Our results are consistent with theories that colour choices are principally mediated by higher level neural processes in the animal brain, since it is at this level physiological signal modulation varies with stimulus modulation in a probabilistic fashion. These functions thus enable important insights into how to model how animals interact with colour stimuli like flowers in complex environments.