Receptor based models for spontaneous colour choices in flies and butterflies

Colour is one of several stimuli used by herbivorous insects in host choice . Insects have between 2 and 5 different types of photoreceptors to catch q uanta of different wavelengths of the spectrum. Many insects have been show n to possess opponent neural interactions between the receptors that enable them to see colour. I present simple models to describe colour choices as functions of the receptor quantum catches and linear interactions of the re ceptor types. Models are applied to data sets obtained from own experiments and from the literature, on Pieris brassicae and P. rapae (Lepidoptera, Pi eridae), Papilio aegeus (Papilionidae), Dacus oleae (Diptera, Tephritidae) and Eristalis tenax (Syrphidae). In fruit flies, detection of green fruit i s based on an inhibitory interaction between a green-sensitive receptor typ e and a blue-sensitive receptor type. This might explain the preference man y herbivorous insects have for yellow over green stimuli. Pollen feeding in hoverflies might have evolved from yellow pollen being a super-normal stim ulus for herbivorous insects. In butterflies, an additional red-receptor is involved in the colour choice for an oviposition substratum and leads to t hem choosing green and not yellow. The models introduced in this study open new perspective for a physiological understanding of the design of visual stimuli for monitoring and trapping pest insects.