Moth wing scale

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Chris S.
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Moth wing scale

Post by Chris S. »

Nothing special here--just an image I want to reference in another thread. It's a wing scale from the sunset moth (Urania ripheus). For those more used to seeing the remarkable, shiny rainbow scales of this insect, be aware that this moth's wings also have areas of very deep black scales that absorb nearly all the light that hits them. This is an example, dark wing scale.

Equipment was a 100x/0.70 Mitutoyo Apo objective on a Nikon D200 camera body. I was testing this lens against another optic with much less working distance, so wanted a flat subject. Unlike the shiny scales of U. ripheus, which are curved, the black scales lie nice and flat. To prepare the scales as test subjects, I plucked a bunch of them from a sunset moth wing with tweezers, and swirled them in 91 percent isopropyl alcohol. Then I plopped an eyedropper's worth of suspended scales on a microscope slide, waited a few seconds for the alcohol to evaporate, and ended up with a nice strew. The scales seem to remain rather doggedly in place without any further fixing or a cover slip, I presume via van der Waals force. Since I was testing on a horizontal rig, the microscope slide was oriented up and down, and the wing scale stayed put very nicely.

Image


What follows is a crop from the above image. It is much tighter than a 100 percent crop--something like 400 or 800 percent enlargement (I didn't record the figure)--upscaled to permit viewing with minimal pixelation. For the picky, please note that we are far into diffraction territory, and my upsizing emphasizes imperfections. This image is not pretty, but serves a purpose.

The thread where I'll reference these images effectively asks what 1/2 micron-sized details look like when photographed in air (not oil), with a long-working-distance objective. So my intent is to show what such details look like in this scenario.

Most spots on this wing scale are a bit less than 1/2 micron. Mitutoyo lists 0.4 micron as the resolving power of this lens. From this demonstration, Mitutoyo's specification seems appropriate.

Image

--Chris

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Post by NikonUser »

Wow, that 2nd image is the best light microscope image I have seen of a lepidopteran wing scale. Has a long way to go but is approaching an electron microscope. Too good an image not to comment on.
Breaking all the rules such as posting an image on another's post and copying an image from the www (not sure about the legitimacy of this).
So, my interpretation (my labels)
image from: http://www.trincoll.edu/~alehman/photobiol210_03.htm
photo of a scale at something like a 45 degree angle, whereas Chris' is looking down on the dorsal surface; his 'spots' are actually spaces between top and bottom layers of the scale and look like windows from above.

Image
NU.
student of entomology
Quote – Holmes on ‘Entomology’
” I suppose you are an entomologist ? “
” Not quite so ambitious as that, sir. I should like to put my eyes on the individual entitled to that name.
No man can be truly called an entomologist,
sir; the subject is too vast for any single human intelligence to grasp.”
Oliver Wendell Holmes, Sr
The Poet at the Breakfast Table.

Nikon camera, lenses and objectives
Olympus microscope and objectives

Chris S.
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Post by Chris S. »

Thanks for this posting, NU. I think your perspective adds a lot of value to this thread.

I had also compared this image with SEM shots, and understood that my “spots” were windows in the lattice formation that forms this wing scale. I was pleased to be seeing—if with far less resolution—features normally shown with electron microscopes. Your inclusion of an SEM image, and notations on it, are very welcome. (And the SEM image you included was not copyrighted, was given proper attribution, and used responsibly for a non-profit educational purpose, much the way it was originally posted to the Net—so it looks like fair use to me.)

Looking at your labels, my brain is having hard time understanding the difference between a “cross rib” and “trabecula.” Would you mind explaining this a bit further?

Thanks much!

--Chris

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Post by NikonUser »

My understanding is that a lepidopteran scale consists of an upper and lower membrane with the lower membrane closest to the wing membrane;
or, put another way, the lower membrane of a scale is ventral and the upper membrane dorsal.
There is an air space between the two membranes except at the edges of the scale where the membranes meet.
The lower membrane is one continuous flat sheet.
The upper membrane consists of a series of longitudinal veins (or ridges) with adjacent veins connected by cross ribs. This upper membrane is incomplete in that it is somewhat like a sieve - full of holes (windows).
The upper membrane is connected to the lower membrane by vertical struts (trabeculae). Not sure where these struts are attached to the top 'membrane'. The SEM image looks like they may be attached to the cross ribs but as labeled they may be shadows; seems more likely that the struts attached to the lower surface of the longitudinal veins.
NU.
student of entomology
Quote – Holmes on ‘Entomology’
” I suppose you are an entomologist ? “
” Not quite so ambitious as that, sir. I should like to put my eyes on the individual entitled to that name.
No man can be truly called an entomologist,
sir; the subject is too vast for any single human intelligence to grasp.”
Oliver Wendell Holmes, Sr
The Poet at the Breakfast Table.

Nikon camera, lenses and objectives
Olympus microscope and objectives

abpho
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Location: Earth

Post by abpho »

Fascinating. Thanks NU and CS.
I'm in Canada! Isn't that weird?

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