Seeing the world through the eyes of a butterfly: visual ecology of the territorial males of Pararge aegeria (Lepidoptera: Nymphalidae)

Combining studies of animal visual systems with exact imaging of their visual environment can get us a step closer to understand how animals see their Umwelt. Here, we have combined both methods to better understand how males of the speckled wood butterfly, Pararge aegeria, see the surroundings of their perches. These males are well known to sit and wait for a chance to mate with a passing females, in sunspot territories in European forests. We provide a detailed description of the males' body and head posture, viewing direction, visual field and spatial resolution, as well as the visual environment. Pararge aegeria has sexually dimorphic eyes, the smallest interommatidial angles of males are around 1 degrees, those of females 1.5 degrees. Perching males face the antisolar direction with their retinal region of the highest resolution pointing at an angle of about 45 degrees above the horizon; thus, looking at a rather even and dark background in front of which they likely have the best chance to detect a sunlit female passing through the sunspot.

Automated summary

Studying the visual systems of animals in conjunction with imaging their visual environment can enhance our understanding of how they perceive their surroundings. The male speckled wood butterfly, Pararge aegeria, has sexually dimorphic eyes and adopts specific body postures to maximize their chance of detecting passing females. By combining both methods, researchers were able to provide a detailed description of the males' visual field, spatial resolution, and behavior in their natural habitat.