What does a fly see?

Something has always bugged me (he he) about the way a flies’ vision is portrayed in books or other media. Flies, as you probably know, have compound eyes. Instead of a big round squishy eyeball like the two you probably have, flies have a whole mess of cones, each one effectively an individual eye (that cannot focus or move) arranged in a mosaic around most of a sphere.

This leads to the issue of how they are portrayed. I’ve used an example based on a Far Side comic, since it is deliberate so I can make my point without being personally critical of anyone. The portrayal is typically something like this:

So here is a question I ask of you. Does the following picture reflect how you see?

A picture of a fly duplicated as if the human eye viewed everything as a mosaic of two images

A fly how a fly might think a human sees a fly based on how a human thinks a fly sees.
© Shouting at the Clouds

Of course not. You see something more like this (ignoring the fuzziness of peripheral vision etc):

A single image of a fly

A fly as a human might really see a fly

Notice the difference? That’s right, your brain mashes the images together so you perceive it as a single image. Why wouldn’t the fly brain do the same thing?

Bonus reference: this link talks in a little bit more depth about how fly eyes work.

If you are wondering where I got the picture from, it is a weird-looking fly I photographed at Angkor Wat in Cambodia. If there are any entomologists out there I’d be interested to know what species it is.

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