Secret Agent Mantis

[MarkSturtevant]

Here are pictures of a big female Chinese praying mantis (Tenodera sinensis). I found her sitting out in plain site in a field one day, and the first picture is as I found her.
Chinese mantis by Mark Sturtevant, on Flickr

So I took her home for a few days for portraits in my photography studio (which doubles as our dining room table).
Mantis eyes by day by Mark Sturtevant, on Flickr

The black spot on each compound eye is called the 'pseudo pupil', and what is weird about them is they always follow you as the mantis turns its head.
Mantis eyes by day by Mark Sturtevant, on Flickr

How does that work? the pseudo pupil is sort of an optical trick. The compound eye is a bundle of units called ommatidia, and each of these has a lens, pigment cells that reflect away light (giving the eye the color that you see), and deep inside are retina cells that absorb light. You are basically looking down into the ommatidia that are pointing at you, and these look black because they don't let much light out in that direction. As the mantis turns its head, you are no longer looking down those ommatidia so you see light reflected off of their pigment cells. Meanwhile other ommatidia are lined up so you are looking into them, and they turn black for the reasons just stated. Hope that is clear!

But all of this changes at night. At night the pigment cells in the eyes of a praying mantis will migrate away (do they move in deep? Not sure), and this is done to let in more light for night vision. What you see is that the eyes look black. It is a bit startling if you have not seen it before.
Mantis eyes by night by Mark Sturtevant, on Flickr
Chinese mantis at night by Mark Sturtevant, on Flickr

In the morning hours, the pigment cells migrate back, and the eye color and pseudo pupil returns.

So... Mild mannered mantis by day...
Mild-mannered mantis by day... by Mark Sturtevant, on Flickr
By night!

[Pau]

Very interesting, Mark!

I never saw those black eyes but looking back to some old Mantis pictures taken after sunset the 'pseudo pupil' seems to be able to change its size
viewtopic.php?p=91001#p91001

[rjlittlefield]

Great images and description!

The dark adaptation is something that I have seen before, but I never succeeded in tracking down the mechanism. Some images and discussion at http://www.photomacrography.net/forum/v ... php?t=3074 .

Another strange thing about the pseudopupil is that if you look at the mantis eye in stereo, the dark spot appears to be deep within the eye, possibly even behind it. This is because the viewer's left eye sees the black spot in one place, while the viewer's right eye, looking from a different angle, sees it in a different place. Images at http://www.photomacrography.net/forum/v ... php?t=3072 and at the links therein. There is some further discussion of the pseudopupil in an earlier thread, viewtopic.php?t=3064 , which also has some recent updates starting at viewtopic.php?p=249651#p249651 .

Insect eyes are fascinating. I find it remarkable how much of their workings was figured out in the 1880's, and by a single person (Sigmund Exner). But there is so much to know, and so difficult to ferret out, the scientific community is still learning details of how they work!

--Rik

[rjlittlefield]

I did some more searching, this time on Tenodera sinensis dark adaptation . A couple of new and interesting references turned up.

In "Complex Worlds from Simpler Nervous Systems", MIT Press 2004, edited by Frederick R. Prete, page 81 in the section titled "In the Mind of a Hunter: The Visual World of the Praying Mantis", by Karl Kral and Frederick R. Prete, appears this paragraph:

The physiological acceptance angle of the rhabdom corresponds to the halfwidth of the rhabdom acceptance function and is expressed as the projection of the rhabdom diameter into space. The total physiological acceptance angle of an ommatidium reaches its maximum in darkness and diminishes with increasing brightness. In dim light it is medium sized, and in dazzling sunlight it is at its smallest. This adaptation to light intensity is brought about by a displacement of pigment at the dioptric apparatus, by a displacement of pigment between the ommatidia, and possibly, also by a change in the rhabdom diameter and the index of refraction between the rhabdom and the surrounding cytoplasm.

This book is listed by Amazon as 464 pages, 2.35 pounds in hardcover. They quoted me a price today of $9.99 for one new hardcover in stock, and I grabbed it. It is supposed to arrive in about a week.

The search also turned up "Spectral sensitivity studies on the visual system of the praying mantis, Tenodera sinensis", available as a free PDF through https://pubmed.ncbi.nlm.nih.gov/5539340/ to https://www.ncbi.nlm.nih.gov/pmc/articl ... pdf/93.pdf . I did not see anything about the mechanism for dark adaptation, but most of the article's content was new to me, both about methods of investigation and mantis spectral sensitivity.

--Rik

[MarkSturtevant]

Very interesting! I do see that Pseudopupils are rather different sized in different insects. Some can be huge. They also change size on the same insect, depending on the angle of view. Probably they are larger in areas that have larger ommatidia (I hope I recall correctly the rhabomeres are more specific, being the area of retina cells that absorb light). In these mantids the Pseudopupil enlarges on the lower front margin of the eyes -- that is they get bigger when they look like they are face on to you but looking down.

[leonardturner]

Remarkable images and most interesting discussion; gradually my understanding improves. My thanks.

Leonard

[jmc]

Wow, what an amazing change to occur daily. Thanks for sharing.

[rjlittlefield]

In "Complex Worlds from Simpler Nervous Systems", MIT Press 2004, edited by Frederick R. Prete, page 81 in the section titled "In the Mind of a Hunter: The Visual World of the Praying Mantis", by Karl Kral and Frederick R. Prete, appears this paragraph:

The physiological acceptance angle of the rhabdom corresponds to the halfwidth of the rhabdom acceptance function and is expressed as the projection of the rhabdom diameter into space. The total physiological acceptance angle of an ommatidium reaches its maximum in darkness and diminishes with increasing brightness. In dim light it is medium sized, and in dazzling sunlight it is at its smallest. This adaptation to light intensity is brought about by a displacement of pigment at the dioptric apparatus, by a displacement of pigment between the ommatidia, and possibly, also by a change in the rhabdom diameter and the index of refraction between the rhabdom and the surrounding cytoplasm.

This book is listed by Amazon as 464 pages, 2.35 pounds in hardcover. They quoted me a price today of $9.99 for one new hardcover in stock, and I grabbed it. It is supposed to arrive in about a week.

Five thumbs up for this book -- it's possibly the most knowledge per dollar that I've ever gotten in print.

That one chapter, containing the above quote, occupies 41 pages in a highly detailed discussion of what's known about the structure and operation of praying mantis. Of particular interest to me was the analysis leading to the observation that binocular vision, of the type that humans use, is not needed to explain how the mantis captures prey. That is, the mantis has no need for comparison of retinal images. Instead, all of its capture behavior can be explained by triggering on the simultaneous appearance of a prey-like stimulus in a small active region of each eye. The operation is rather like the crossed-laser systems that we use for camera triggering, with the refinement that each eye's absence/presence signal depends on size and movement detectors working on the image stream from just that one eye. As the book says, "The system is actually most elegant in its simplicity."

Other chapters of the book address vision in jumping spiders, honeybees, amphibians, butterflies, crayfish, mantis shrimp, and octopus, plus there are a couple of chapters on touch and sound. Fascinating stuff -- way waay more than I will ever be able to remember in any detail.

Amazon says that used copies are still available from a number of suppliers. I recommend to get them now, while you can.

--Rik

[BugEZ]

Rik wrote favorably about “Complex Worlds from Simpler Nervous Systems”. I must second his strong endorsement. After reading the very enlightening discussion on jumping spiders I shall never look at them the same way!

Keith

[dunksargent]

In "Complex Worlds from Simpler Nervous Systems", MIT Press 2004, edited by Frederick R. Prete, page 81 in the section titled "In the Mind of a Hunter: The Visual World of the Praying Mantis", by Karl Kral and Frederick R. Prete, appears this paragraph:

The physiological acceptance angle of the rhabdom corresponds to the halfwidth of the rhabdom acceptance function and is expressed as the projection of the rhabdom diameter into space. The total physiological acceptance angle of an ommatidium reaches its maximum in darkness and diminishes with increasing brightness. In dim light it is medium sized, and in dazzling sunlight it is at its smallest. This adaptation to light intensity is brought about by a displacement of pigment at the dioptric apparatus, by a displacement of pigment between the ommatidia, and possibly, also by a change in the rhabdom diameter and the index of refraction between the rhabdom and the surrounding cytoplasm.

This book is listed by Amazon as 464 pages, 2.35 pounds in hardcover. They quoted me a price today of $9.99 for one new hardcover in stock, and I grabbed it. It is supposed to arrive in about a week.

Five thumbs up for this book -- it's possibly the most knowledge per dollar that I've ever gotten in print.

That one chapter, containing the above quote, occupies 41 pages in a highly detailed discussion of what's known about the structure and operation of praying mantis. Of particular interest to me was the analysis leading to the observation that binocular vision, of the type that humans use, is not needed to explain how the mantis captures prey. That is, the mantis has no need for comparison of retinal images. Instead, all of its capture behavior can be explained by triggering on the simultaneous appearance of a prey-like stimulus in a small active region of each eye. The operation is rather like the crossed-laser systems that we use for camera triggering, with the refinement that each eye's absence/presence signal depends on size and movement detectors working on the image stream from just that one eye. As the book says, "The system is actually most elegant in its simplicity."

Other chapters of the book address vision in jumping spiders, honeybees, amphibians, butterflies, crayfish, mantis shrimp, and octopus, plus there are a couple of chapters on touch and sound. Fascinating stuff -- way waay more than I will ever be able to remember in any detail.

Amazon says that used copies are still available from a number of suppliers. I recommend to get them now, while you can.

--Rik

Just ordered a 'used' copy of the book for £8 inc. UK shipping ... thank you Rik ... several more used copies listed by Amazon UK

BW

dunk