By chance?

[Gawdzilla Sama]

They can also be used to flavor soups. I prefer yakisoba.

[Mister Agenda]

Sigh. Huxley and Sagan were great science educators. But the current Chief of the Division of Invertebrate Studies and Curator of Crustacea at the Los Angeles County Natural History Museum (Joel W. Martin, PhD Marine Biologist with numerous books and articles to his credit, mainly about the natural history and evolutionary relationships of decapods and brachiopods; got his bio off Wikipedia) considers Huxley and Sagan's story about how the heikegani 'probably' came to so resemble angry samurai's via enhancement of a faint resemblance by superstitious Japanese fishermen to be a modern myth. The pattern of ridges are functional as muscle attachment points and similar patterns are found on the carapaces of other species and in the fossil record. I think I'll go with a relatively obscure but actual expert and specialist on the matter over famous but more generalist science popularizers in this particular case, despite my gratitude for their many accomplishments and contributions. They didn't study the heikegani, they knew of it and proposed a reasonable explanation for its unusual carapace pattern. That explanation happens to be incorrect.

[no one]

I'll bet all this talk of crabs, has our dear tater tot whispering sweet nothings to his pubic companions.

[Yukon_Jack]

“And by the way, those butterflies with 'perfect owl eye' wing patterns are not even 100% effective against being eaten by their predators.”

Thank you, but that is not my point.
I stress the incredible chances that perfect owls eyes to even manifest on a butterfly’s wings in the first place and did it happen all at once? Did just the irises form first, one then the other? Partially?Or did just one outer eye form fully first? Did they mutate in steps if they weren’t the right distance apart? We’re they The wrong color before they became the right color? Ever ask yourselves these questions?
the Katydid looks like a perfect walking leaf and by 100% chance mutations. The honest mind would have a serious pause considering all this

[arewethereyet]

Wouldn’t perfect owl eyes be able to see?

[downbeatplumb]

“And by the way, those butterflies with 'perfect owl eye' wing patterns are not even 100% effective against being eaten by their predators.”

Thank you, but that is not my point.
I stress the incredible chances that perfect owls eyes to even manifest on a butterfly’s wings in the first place  and did it happen all at once? Did just the irises form first, one then the other? Partially?Or did just one outer eye form fully first? Did they mutate in steps if they weren’t the right distance apart? We’re they The wrong color before they became the right color? Ever ask yourselves these questions?
the Katydid looks like a perfect walking leaf and by 100% chance mutations. The honest mind would have a serious pause considering all this

The answer is that they evolved bit by bit. 

There you go. That was easy.

[Fake Messiah]

the Katydid looks like a perfect walking leaf and by 100% chance mutations. The honest mind would have a serious pause considering all this

[Gawdzilla Sama]

“And by the way, those butterflies with 'perfect owl eye' wing patterns are not even 100% effective against being eaten by their predators.”

Thank you, but that is not my point.
I stress the incredible chances that perfect owls eyes to even manifest on a butterfly’s wings in the first place  and did it happen all at once? Did just the irises form first, one then the other? Partially?Or did just one outer eye form fully first? Did they mutate in steps if they weren’t the right distance apart? We’re they The wrong color before they became the right color? Ever ask yourselves these questions?
the Katydid looks like a perfect walking leaf and by 100% chance mutations. The honest mind would have a serious pause considering all this

Magic is a better answer?

[Ranjr]

A dipole magnetic field lines make owls eyes.  That is, when a person looks at the image and makes the connection.

[arewethereyet]

We are wired to look for patterns.

I have a photo I took of a tiger at a local big cat rescue. He is sitting in a tank of water facing away from me. Each of his ears has a white circle almost perfectly centered. The first thought is that maybe they are there so that prey or a rival sneaking up behind will think they are eyes - but, other than humans how many predators do tigers really have to worry about. Another theory is that it helps cubs be able to follow their mother in tall grass. But since the males also have these flashes that second theory could be argued. Humans jump to eyes because of pattern seeking.

I have also read that they may signal aggression when the cat turns its ears forward - it's tiger warning for back off. So there are some theories but unless a tiger tells us I don't suppose we will ever know with certainty.

It was interesting to research though.