Remarkable red colour vision in two Mediterranean beetle pollinators.

Abstract

Beetles are one of the most species-rich insect orders and a primeval pollinator group, but much remains unknown about their sensory ecology. Glaphyrid beetles have a strong association with specific Mediterranean flowers, especially red, bowl-shaped flowers, suggesting an ability to see red colours. What is the physiological basis of the red sensitivity in Glaphyridae, and how does their ability to see red colours shape flower evolution in the Mediterranean? We investigated the glaphyrids Pygopleurus chrysonotus and Pygopleurus syriacus using electrophysiology, behavioural experiments and colour trapping. Intracellular recordings of photoreceptors revealed the presence of four photoreceptor types with peak sensitivities in the UV, blue, green and red wavelength ranges. Experiments in the field with P. chrysonotus demonstrated the behavioural use of colour vision to detect red targets as well as a clear preference for red colours. Glaphyridae represent an emerging model system for studies on beetle visual ecology and evolutionary tuning of (flower) signal production and detection by pollinators.