Eyes: Insects in General:
Skin: Frog skin:
Mayfly (Centroptilum cf elongatum)
Retired Professor of Anatomy, Ian Gibbins, has kindly shared his thoughts with us to help people learn:
Somewhere I vaguely remember reading about the function of those split eyes. Many insects have compound eyes that are effectively split into different zones with different optical properties / light sensitivities, usually for seeing different things above and below them. You can often see the difference in dragonfly eyes, but its really extreme in mayflies.
Meanwhile, it's worth remembering that many creatures have split visual systems eg the various eyes in spiders, with the mediam anterior two usually specialsed for colour and detail, the rest more for movement detection... which is actually not very different from our own eyes...
The human retina is effectively two concentric light detectors => the inner part is high resolution, colour; the outer part is mostly monochromatic, low light movement detection.