Biocurious: Amateur Entomology: Insect Wing Nanostructure

Amateur Entomology: Insect Wing Nanostructure

Posted 30 July 2006 by Andre under Biocuriosities & Andre's Research

dorsal shot of insect ventral shot of insect It is well known, and well documented, that butterflies and moths have beautifully microstructured wings that give rise to their iridescent colours. It’s easy to find pictures of these structures and studies of their colour production and other optical properties. What I’ve been having a harder time learning about though is the nanostructures found on some other insect wings.

This story starts, as others have before it, with a walk around campus during an otherwise regular work day. The ground treasure that caught my eye this time was a dead, but externally undamaged, insect with widely separated eyes, a green and brown body, and clear colourless wings supported by small black fibers running through them. I’m totally ill equipped to identify this specimen so I will pass that responsibility on to you. What species is this? It’s pretty big and I’ve seen a couple on the ground in Philadelphia in the last couple of weeks so it can’t be too obscure. The Academy of Natural Sciences in Philadelphia has an entomology department so I’ll ask someone there and keep you updated on the response. In the mean time, if you recognize this insect, let me know in the comments.

What I’m even more interested in is what I found when I put the wing under an AFM. The surface is densely covered with nanoscale bumps about 150 nm in diameter! nanostructure of insect wing surface

The pattern is regular, in some regions approximating a hexagonal lattice. Are these common features of insect wings? What purpose do they serve? Do the bumps reduce the contact area available for the binding of particles making them easier to dislodge? Does the topography control wettability making a surface that is more hydrophobic than would be possible using smooth waxy excretions alone? Hydrophobicity could be a big advantage for insects that want to fly in the rain or that live around water. A film of water could significantly increase the mass of a very thin wing afterall. Does anyone know, or have other ideas?

The varied morphology of insects is fascinating, but most people, myself included, aren’t aware of the finer structure that can’t be seen by eye or even with an optical microscope. I wonder what else are these incredible material scientists hiding…

Bill Hooker 31 July 06 #

It’s a cicada—can’t say what species. The wikipedia entry is a pretty good primer, until your entomology colleagues can fill you in on specifics.

At 150nm, the bumps are starting to approach the size of large biomolecules—they are a little bit too big for single molecules, but aggregates/complexes could reach that size.

I have only one idea you didn’t have already, but it doesn’t seem very likely to me: cicadas use their wings as secondary sound production organs (secondary, that is, to the tymbals). The bumps might provide friction or some other structural quality important for sound generation.
Andre 31 July 06 #

Thanks for the tip. I went to the Wikipedia entry and as I feared, they were described as “one of the most widely recognized of all insects.” My only defence is that they don’t live in Newfoundland… as far as I know!

I also like the acoustic angle.
Hank Roberts 31 July 06 #

These folks might appreciate your picture:
...
Cicadas have three different mechanisms for producing their song ranging from specialized tymbal structure to stridulation and simple wing clapping. ...
www.insects.org/entophiles/homoptera/homo_006.html
Bill Hooker 31 July 06 #

Cicadas stridulate? I thought they just clapped/flicked their wings. Maybe there’s more to the acoustic idea than I thought.

My favourite guess so far is hydrophobicity, though. Those bumps look as though they might form a surface on which water would ball up rather than wetting it: surface tension would keep a tiny ball of water balanced on the tips of the bumps rather than letting it run down into the valleys.

I don’t suppose you can view tiny water droplets with an AFM…?
Andre 1 August 06 #

I can’t image water droplets, but I could make contact angle measurements before and after a treatment of acetone to disrupt the surface (including, of course, AFM imaging to monitor the affects of the acetone). Could be interesting. Maybe I’ll have to find another cicada!
Bill Hooker 1 August 06 #

Insect wings are, I think, made primarily of chitin—I don’t know how much protein is also present. Acetone will denature protein, and probably won’t do chitin (a polysaccharide, similar to cellulose) much good either. If the epicuticle (see wikipedia again) extends over the wing surface—as one of the papers below indicates—then the outermost layer is hydrocarbon, which will probably also be stripped by acetone.

Turns out that insect wings have been fairly well studied, because insect flight is not well understood. Here are a few papers that look like a good starting point:

http://arjournals.annualreviews.org/doi/abs/10.1146/annurev.en.37.010192.000553
http://www.springerlink.com/openurl.asp?genre=article&id=doi:10.1114/1.1424921
http://dx.doi.org/10.1016/j.asd.2004.05.006

All are, unfortunately, pay-access, and my school doesn’t subscribe.
Uncle Al 1 August 06 #

Vacuum gold deposit and have a bitchin’ emitter plate!
Andre 1 August 06 #

for educational use:

http://arjournals.annualreviews.org/doi/abs/10.1146/annurev.en.37.010192.000553
http://www.springerlink.com/openurl.asp?genre=article&id=doi:10.1114/1.1424921
http://dx.doi.org/10.1016/j.asd.2004.05.006
trrll 2 August 06 #

In your defense, you are not the only person who cannot immediately recognize a cicada. I recall an occasion in the NY subway, when I saw a knot of people fearfully exclaiming, “Eeuuw, what is it? Kill it! Kill it!” Curious, I approached and found them surrounding a cicada. So I simply scooped it up and kept walking, hearing behind me horrified cries of “Eeuuw, he touched it!” Cicadas, despite their imposing appearance, are harmless, and I think they are quite beautiful. I simply carried it with me, buzzing loudly, until I was able to release it. It was the only time I’ve seen a cicada as far north as NY. In Houston, where I grew up, the trees at night are buzzing loudly with them.
Peter McGrath 2 August 06 #

Could it be to do with turbulence reduction and aiding flight? Maybe air behaves more like a liquid when you’ve got such light wings trying to power through it and (like shark skins) the nanoscale bumps (nice phrase) smooth the airflow.
Will M. 3 August 06 #

How about a structure similar to the dimples on a golf ball?
Hank Roberts 3 August 06 #

Oops, I [thought I] posted a link in #3 to a web page of insect, including cicada, photographs; was it deleted? is it invisible? anyhow, I do think yours would be welcome additions to such online compilations if you’ll offer them.
Andre 3 August 06 #

Peter and Will:

I was also wondering about that but I think the bumps in this case are too small compared to the scale of the wing to have an effect on the turbulence but if you know about aerodynamics please correct me.

Hank:

The link is there in text form. The site looks pretty good but I don’t know that they would be interested in my images. If they were, I would offer them provided they remained free to use.
Peter McGrath 5 August 06 #

Know about aerodynamics? I still think it’s magic every time I’m a plane I’m in gets off the ground.
Dan 27 March 07 #

I’m 99% certain that’s a Tibicen chloromera. I run a web site called Cicada Mania with hundreds of photos of cicadas http://www.cicadamania.com/cicadas/category/tibicen/
Andre 27 March 07 #

Thanks for the identification and the informative site, Dan.
milagros 16 July 07 #

Hi my name is Milagros Matthews new orlean today i saw this bug like the one on you picture out side of the door and i did nkow what was it so i took a Broom and i move it it was very loudly sound. i want to know if that bug bite and tell me the sign of it.
zik4o 7 October 07 #

This maybe in help of you… :)
...I was examining the chitin shells of insects under my microscope in the summer of 1988 along with their pinnate antennae, the fish-scale microstructure of butterfly wings, iridescent colors, and other inventions of nature. I became interested in an amazingly rhythmical microstructure of one large insect detail. It was an extremely well-ordered composition, as though stamped out by factory equipment according to special blueprints and calculations. As I saw it, the intricate sponginess was clearly unnecessary either for the strength of the part, or for its decoration. I have never observed anything like this unusual micro-ornament either in nature, in technology, or in art. Because its structure is three-dimensional, I have been unable to capture it in a drawing so far, or a photograph. Why does an insect need it? Besides, other than in flight, this structure at the bottom of the wing case is always hidden from the eye. No one would ever see it properly. Was it perhaps the wave emitter using “my” multiple cavity structures effect? That truly lucky summer, there were very many insects of this species and I would capture them at night. I was not able to observe these insects neither before, nor later. I placed the small, concave chitin plate on the microscope stage in order to again examine its strangely star-shaped cells under strong magnification. I again admired this masterpiece jewelwork of nature. I was about to place a second identical plate with the same unusual cell structure on its underside almost purposelesly on top of the first one. But then! The little plate came loose from my tweezers, hung suspended above the other plate on the microscope stage for a few seconds, then turned a few degrees clockwise and slid to the right, then turned counterclockwise and swung and only then it abruptly fell on the desk. You can imagine what I felt at that moment. When I came to my senses, I tied a few panels together with a wire and it wasn’t an easy thing to do. I succeeded only when I positioned them vertically. What I got was a multi-layered chitin block and I placed it on the desk. Even a relatively large object, such as a thumbtack, would not fall on it. Something pushed it up and aside. When I attached the tack on top of the “block”, I witnessed incredible, impossible things. The tack would dissapear from sight for a few moments. That was when I have realized that this was no “beacon,” but something entirely different.
from the article: http://www.rexresearch.com/grebenn/grebenn.htm

Please, e-mail me if there is a connection with your results?
Kichiza 13 October 07 #

Antireflection Microstructures ?

http://www.wft.bz/pdf/Moth-Eye_Specs.pdf
Victoria Càceres 23 October 07 #

Have you ever seen the structure of a fly rostrum? or the intensity of the colours in the wings of Calliphoridae sp, flies are the most exciting creatures, take a little look of their bodies parts and rareties, you will find some interisting physical adaptations on flies, who leads to uncommon features into a common insect.
Daniel 28 May 08 #

I sense, as with Peter McGrath, that it could be an aerodynamic aid, especially when you think of the fact it is operating in ultra low Reynolds numbers. The surface could be, depending on the rate of motion and frequency of the wings movement, operating like the surface of a golf ball with all it’s dimples. Pimples have a similar effect. It could possibly work if the wing bends into a convex on the downward flap action. All this assuming there is no other type of epicuticle layer separating the air molecules from this hexagonal surface matrix. Humans are beginning to take more interest in the flight characteristics of animal ornithopters and insecta. The surface, I agree with the previous statement, could be used for sound production also. There is certainly going to be some interesting boundary layer effect. If only you could see the wing move within the viscous relativity at such high magnification and at extremely slow speeds.
Bonnie 26 June 08 #

I just found a bug that looks just like this one. I live in North Carolina. Help! I have a picture of it, if there’s a email I can send it to please let me know.
Brittany 3 August 08 #

2 of my children and i were sitting outside on a hot Sunday morning while my son walked along the brick landscaping around our front porch when he pointed out this extremely large green insect that at first startled me a bit, but upon inspection, it was latched onto a cacoon type of thing…well really it looked like the shell of another insect, brown all-over without wings. My children and I were just curious as to whether this winged insect actually came out of this cacoon-like shell. Thanks from Indiana

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Amateur Entomology: Insect Wing Nanostructure

Posted 30 July 2006 by Andre under Biocuriosities & Andre's Research