how do bugs eyes work….specifically flies and dragonflies. Like what do they actually see and how does it work?
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coordinating the vision of compound eyes would seem to be more basically functional if you were prey but to fine tune this complexity for a predator, wow!
They have “compound eyes.” Their eyes are made up of thousands of tiny lenses. The simplest way to explain how they see is each lens is a tiny portion of a larger picture sort of how many pixels make up an image on a screen. This way the insect has a very wide range of vision.
The downside to insect compound eyes is that they can’t control how much light enters their eyes, humans have pupils that can control how much light to let in. That means insects are extremely near-sighted. On average, they can only see a few yards away.
The upside to compound eyes is that it’s extremely good for differentiating movement. They can react to movement much more quickly.
I think it’s biologically more efficient many small eyes than a single large one and also for redundancy purposes
Having eyes setup in such manner is what provides them 360° view
On a similar subject, a question that I often think about. Some insects have great eyesight, with highly refined ‘hardware’. The question I think about is the ‘software’ behind it. How do they process the information they receive from their eyes? Are they able to think about what they are seeing and calculate what to do next, or is it entirely instinctive? If they see something moving are they able to identify it as a predator or potential food before deciding to run or attack, or are they entirely pre-programmed reflexes?
Some insects and arachnids can carry out highly specialised tasks, I watched a spider spinning a highly intricate web and tried to read about it. Apparently they don’t “know” that they are doing it, it’s entirely instinctive in the same way that we breathe without thinking about it. I just find this really hard to comprehend through the eyes of a human, is there really no thought or emotional responses? At what point in the Tree of Life did animals evolve the ability to make decisions and have abstract thoughts?
It’s an incredibly well studied field, but this makes it a minefield when trying to find papers and journals because there are so many and some directly contradict each other.
Your eyes contain a lot of light sensitive cells on the back of the eye and a lens with a single small hole (pupil) in the front of the eye. The size, shape, curvature, and material the eye lens is made of create a situation where light from some particular direction that passes through the pupil lands on only one of the light sensitive cells.
But that design doesn’t scale down to small sizes very well. For instance, there has to be some distance between the lens and the photoreceptor. That distance can be pretty small if you make the lens out of high-refractive-index glass – like on your cell phone. But if the refractive material is organic it’s not going to be as good.
So compound eyes use a different method to make sure each photoreceptor cell only gets light from some particular direction. Each photoreceptor is at the bottom of a deep, narrow well. So it’s like looking through a long tube — it only gets light from the direction the tube is pointed. So each photoreceptor gets it’s own narrow tube and all the tubes point in different directions. The tubes are kind of cone-shaped — narrower at the bottom and wider at the top. And they’re stacked very close together, so the top looks like a honeycomb or similar pattern. Of course, there’s a transparent covering over the top to keep germs out and I think the tube is filled with a clear liquid similar to our eyes.
That design isn’t as good as your eye — the fact that there’s a structure built up around every photoreceptor means they have to be spaced out. And the number of “pixels” the insect eye can see is equal to the number of tubes. Also, all the light from some distant point source has to go through that one narrow tube that’s pointed the right way. Light that hits the other tubes just gets absorbed on the tube’s black inside walls. Compare that to your eye — at night, your pupil can be maybe a centimeter in diameter and all the light that hits that centimeter get’s bent so that it all goes to one cell.
So the horror movie trope of “lots of identical images in an array” is wrong. A better trope would be a medium-to-low-resolution image that’s really only sensitive to things that are fairly close.
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