# black dot on eyes movement?



## Johnald Chaffinch (Oct 25, 2005)

how do some mantids eyes reflect a black dot right back at you, no matter where you are relative to the mantis?


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## ibanez_freak (Oct 25, 2005)

Hi,

I heard somewhere that that's where the light collects or something. but can't be other wise it would only appear in one spot. Must have something to do with the human eyes as well.

Cheers, Cameron.


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## Samzo (Oct 25, 2005)

This has no factual base behind this but i reckon they eye is like perfectly in the centre so where ever you are it sees you... i really dunno lol its kinda creepy though


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## ibanez_freak (Oct 25, 2005)

Yah, when me and my brother first got mntis we thoughtthey were pupils and had a huge argument about who it was staring at. He he, kinda took us a whileto realise  .

Cheers, Cameron.


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## Johnald Chaffinch (Oct 25, 2005)

someone here is bound to know.

compound eyes have loads of ommatadia lenses which usually seem slightly reflective and dome shaped on the outside, so i assume it's something in the way that only a small surface area of the eye will be reflecting right back at you ( because of the effect of the way domes reflect ). i think maybe i've answered my own question

:wink:


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## Rick (Oct 25, 2005)

The way I understand it it's the exact spot light enters as you look straight on at the mantids eye. Or something like that :?


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## Johnald Chaffinch (Oct 25, 2005)

> The way I understand it it's the exact spot light enters as you look straight on at the mantids eye. Or something like that :?


you mean that you're looking right down one of the lenses - hence it appears black, like a pupil does?

ask someone to look at a mantids eyes with you, them looking from the other side of the mantis. you'll both find that the dot seems to be pointing at you both simultaneously, bafflingly


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## Rick (Oct 26, 2005)

> > The way I understand it it's the exact spot light enters as you look straight on at the mantids eye. Or something like that :?
> 
> 
> you mean that you're looking right down one of the lenses - hence it appears black, like a pupil does?
> ...


Oh I know. I've done that before. It's like the exact spot of the eye where you are looking at.


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## Ian (Oct 26, 2005)

"The mantis has compound eyes with hundreds of individual optical elements known as facets. A discussion of its eye alone could easily occupy a separate article. This design gives the mantis a view that is almost 'all round' effective, allows both near and far vision, and sensitive detection of motion. Both eyes cooperate to focus on the same target. This allows extremely effective tracking of small and fast objects."

Cheers,

Ian


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## Johnald Chaffinch (Oct 26, 2005)

havent reached a conclusion yet :|


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## Johnald Chaffinch (Oct 26, 2005)

does a mantids eye dot always point towards you, or does it sometimes move when you're both stood still?


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## FieroRumor (Oct 26, 2005)

I belive the "dot" is where the optic nerve enters the eyeball area...?

I love the dot, it gives the Mantis such a look of intelligence, like it's lookin' ya in the eye...


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## Johnald Chaffinch (Oct 28, 2005)

that's not it either, i watched that 'Alien Insect' documentary to check it out again, seems it's definitely near the surface and seems exactly like any ray of light reflecting off of the eye, except that it's not because it's black! and small. bizarre. someone must know... :|

i'm suspecting the only answer must be that it's that from the position you're in you'll be looking down one or two lenses of the eye, and they'll appear black like a pupil does.

here's an example of it :







^ it's head reminds me of the atmospheric bands on jupiter - and the black dot like the giant storm spot. uncanny


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## White Owl (Oct 30, 2005)

im not mantid pro, but to me that seems to just be his eyeball.


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## Johnald Chaffinch (Oct 30, 2005)

they dont have eyeballs like we do they have compound eyes, like this :






there's no moving part, yet on some mantids a small black dot can be seen in different positions on the eye depending on where you're looking from!?


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## Joe (Oct 31, 2005)

A mantis's compound eye is made up with thousands of ommatidums, all connected to the visual receptor center. Imagine a thousand telescopes attached to ur eye all facing in different directions to form a dome shape like the mantid's eye, looking like the cross section Johnald has, no matter with end u look at of each lens, they will all show a black dot because of each ommatidium leading stright to the visual receptor center, and since all these ommatidium are extremely small and can be seen through the human eye over a larger area, this makes you look through maybe hundreds at a time wich makes the black dot bigger. but being limited to looking through a little amount of ommatidium lenses directly because of the dome shaped eye, this limits the black dot's size. if the compound eye were completely flat and no angles at all, the black dot would cover the whole area because all the lenses would be facing u directly. All athropods have these type of compound eyes and have the same effect.

Joe


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## Johnald Chaffinch (Oct 31, 2005)

at last  

thankyou joe


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## Ian (Oct 31, 2005)

wow Joe, nice one!

Cheers,

Ian


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