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#3: Compound Eyes




Litinsects #3: Compound Eyes

I spy with my little eye. Eyes have evolved independently numerous times, which is why they vary so greatly in form and function depending on the organism (notice how I said organism and not specifically animal...? Well it depends on how eyes and sight are defined but animals are not the only life forms that can “see”). 

Insects 🐝 and their close relatives the crustaceans have COMPOUND EYES, which are these multi-faceted eyes that you’ve probably seen in flies... So how do they work?

  • Compound eyes are composed of units called OMMATIDIA, which are usually hexagonal in shape. A single ommatidium is like a mini eyeball: it contains photoreceptor cells, a lens, pigments, and an axon bundle that provides the animal’s brain with a small section of the picture that’s in front of it. The brain puts together the visual information from all ommatidia, forming just one image. So flies don’t actually see the world as a kaleidoscope like they sometimes show in movies
  • The number of ommatidia in an eye affects how detailed the image is. This number can range from a few (in silverfish) to around 30,000 (in dragonflies), depending on how important sight is to the insect’s lifestyle
  • Most compound eyes don’t see in very high resolution but are great at sensing RAPID MOVEMENT and come with a huge range of vision (almost no blind spots). That’s why flies always see you coming and are outta there before you can ever swat them
  • Insects usually can’t see the colors red and orange but many can see into the UV spectrum and even polarized light
Guess what? Insects actually have ANOTHER type of eye too! Be on the lookout 👀 for tomorrow’s post, where I’ll tell you all about it!
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