Previous to this question, I made a post regarding many questions about the biology of the creature I had been designing. Looking back on it, I realized that I asked a LOT of questions for just one post and did not go into very many specifics. I decided to break those questions up and go into more specifics on what exactly I was looking for, with this question regarding the compound eyes of my creatures.

I'll start off by giving some quick background. These creatures are insect-looking bipeds that have evolved on a mostly jungle/ocean planet with various (not very large) grasslands surrounded by these jungles, justified (from what I've read) by a thick nitrogen/oxygen/carbon-dioxide and humid atmosphere, significant amounts of water, continents mostly placed near the equator, and possibly a slower planetary rotation/adjusted tilt. These creatures are mostly predatory, developing and embracing an elite warrior culture and are likely the best soldiers and warriors in the galaxy, almost always outmatching any other galactic creature or society in combat. These creatures on average are around 7.5 ft tall and weigh roughly 200+ pounds, but these measurements are flexible to change if necessary.

I imagine these creatures' eyes being or looking like compound eyes with human-like vision quality (having decent to good visual acuity/possess depth perception and the ability to focus on objects) or better. Based on my brief research into compound eyes, most animals that have them (insects and crustaceans) aren't the best in terms of visual acuity, depth perception, and focus ability due to the way compound eyes on Earth are structured. Although some insects such as the dragonfly have decent vision due to their compound eyes consisting of over 30,000 facets, their visual acuity is still inferior to that of, say, humans. One article I came across while looking into this subject even claimed that the visual acuity of human eyes was still over 100 times better than that of dragonflies.

As for the size of the eyes compared to that of the head, in addition to facial structure, I would assume that of the Asian Giant Hornet is the closest to what I have in mind. Assume that the size/structure would be scaled up to that of the height provided.

My question is: How could the structure of the compound eyes possessed by these creatures be modified or adapted to allow for the traits previously described, all while retaining the appearance of compound eyes? Is it even possible to do so?

  • $\begingroup$ Hello MinimumReaction. I suggest linking to the articles you read in the question, so that we can make an analysis and either confirm them and propose alternatives, or rebuke them. For the record mantis-shrimp eyes are also compound (though not like insects') and they have trinocular vision in each eye, as well as being able to process light in up to 12 channels compared to our puny four. $\endgroup$ – Renan Oct 22 '18 at 19:49
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    $\begingroup$ You might want to check out the Bold Jumping Spider, which has unparalleled depth perception in spite of its compound eyes. In spite of their small brains, they are intelligent enough to have individual personalities and some individuals even enjoy playing with humans $\endgroup$ – pojo-guy Oct 23 '18 at 2:05
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    $\begingroup$ @pojo-guy Although the suggestion is appreciated, further research into Bold Jumping Spiders suggests that the principle eyes in these spiders (their main vision eyes) are simple eyes and not compound eyes like that of insects. Unless I am mistaken and there are exceptions, my research leads me to believe that spiders do not have compound eyes like I'm referring to in my question. $\endgroup$ – MinimumReaction Oct 24 '18 at 16:56
  • $\begingroup$ @MinimumReaction I learned something new today. Thank you! $\endgroup$ – pojo-guy Oct 25 '18 at 2:50

Compound eyes have a single retinal cell per facet, each with its own lens. To offset the acuity issue, pack them in more densely: humans have fairly acute vision, but an eagle's vision put that to shame with its 5x higher foveal density.

With compound eyes, there are no ciliary muscles to reshape the lens and focus the image onto the retina. Instead of making all of the facets identical, make the lenses have different focal lengths and arrange them into visual units. If these lenses are somewhat diffuse, each visual unit will have a retinal cell that will be excited by a relatively non-overlapping range of distances (eg. 2-20mm, 1-10 cm, 5-50 cm, 25-200cm, 1-5m). Each visual unit can interface with a horizontal cell to limit the visual overlap. This more complex architecture will probably require more brain space than our own visual cortex.

I'm not sure if you want to get into the developmental biology, but a system like this seems feasible. Each visual unit can begin as a single retinal cell, which divides a couple of times and later differentiates

As far as justification goes, make the planet darker than Earth to increase the number of rods and cones required for functional vision. Compound eyes show up in both predatory and prey insects; your example of dragonflies sounds similar to the niche these beings inhabit

  • $\begingroup$ Thank you for the post, although there is one part I'd like clarification on. By "...packing them in more densely", what exactly are you referring to? Are you suggesting that there be more facets within each eye? Packing the retinal cells more into each facet? Or are you referring to something else? The wording just seems a little unclear. $\endgroup$ – MinimumReaction Oct 23 '18 at 0:23
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    $\begingroup$ Whoops, my bad. I meant a high facet density, each with a single retinal cell $\endgroup$ – Punintended Oct 23 '18 at 16:51
  • $\begingroup$ Would having more ommatidia in each compound eye (due to the compound eyes being larger overall) also assist in improving visual acuity? Would it be better to make the ommatidia larger instead? $\endgroup$ – MinimumReaction Oct 25 '18 at 15:03
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    $\begingroup$ Larger ommatidia wouldn't really help - you could increase the number of retinal cells per from one to multiple, but that defeats the purpose of a compound eye, especially since each cell would have non-optimal focus due to the lens optics. AFAIK, you want each ommatidium as small as possible (without changing the biology of the retinal cells) so that you can pack more of them into each eye $\endgroup$ – Punintended Oct 29 '18 at 20:13
  • $\begingroup$ Just what I needed to know! Thanks! $\endgroup$ – MinimumReaction Oct 29 '18 at 23:28

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