Until the colder weather arrived a couple of days ago we had several red admiral butterflies in the garden. I took some extreme close-ups of them, while they were feeding on ripe pears, and noticed in the images .....
.... that their eyes have this strange hexagonal pattern. Looking closer still, it's clear that .....
.... the eye surface is hairy and it looks like it's the pattern of hairs, located in between the individual ommatidia of their compound eyes, that is responsible for those large pale hexagons. A comparison with eyes of other common butterflies, like...
..... this small white, shows a pattern of darker patches on the eye but not a hint of hairiness around the ommatidia.
So I wonder what the hairs' function might be? Maybe they enhance flicker vision - the sensitivity of compound eyes to movement of objects across the field of vision............?
Hairy eyes are not uncommon in insects - click here, for example, to see a scanning electron micrograph of a honeybee's hairy eye. Another possibility of that the hairy surface might stop pollen sticking to the eye surface in these flower-visiting insects.........
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