This is a photo of an alpine black swallowtail butterfly (Papilio maackii) from China, showing the scales that cover the underside of the forewing. The butterfly here is a male, summer version (I believe the females have more red scales on the topside of the hindwings)(2).


Detail view.




Approximate Photo Location (Underside)


Magnification: 4X

Field of view: ~3/8” x 1/4” (9.0mm x 6.0mm)

Images in focus stack: 18


Colorful blue and green scales can be found on the topside of this butterfly. The orange “glowing” effect in the image above is caused by the flash behind (back-lighting) the wing.

The alpine black swallowtail butterfly can be found in China, Russia, Korea, and Japan (1). Two generations are born each year–one in the spring and the other in summer; the summer version is roughly 1.5 times larger in size (1, 2, 3). As detailed in the photo above, this butterfly has vibrant blue and green scales on the topside of its wings. These colors are produced by the structural features of the scales rather than pigmentation (4). In pigmentary color, certain wavelengths of light are absorbed by the material, and the color we perceive is what is reflected or transmitted back to us (5). Chlorophyll, for example, fuels a plant by absorbing light in the blue and red areas of the spectrum (the pigment reflects yellow/green light)(5). In structural color, the color is produced by the reflection/deflection of light through a structural form without essentially any loss of energy (7). Structural colors can look iridescent and change with the viewing angle, or look more diffuse (6, 7). To give you an example, the blue morpho butterfly has brilliantly colored blue wings, but if you grind the wings up (and destroy the original structure), they turn grey or brown (8, 9). These two color production methods are not mutually exclusive. Some snakes and frogs, for instance, combine yellow pigments and blue structural features to appear green (6, 8). When these animals die, the pigments degrade and the animals then “turn” blue as the structural features remain (8, 10).


1. Khramov, P., Pozhogin, D., Nikulina, I., & Kotov, S. (2014). Papilio maackii Menetries, 1859. Retrieved from

2. DK, Wilson, D.E. (2015). Wildlife of the world. New York: Penguin Random House. Retrieved from Google Books.

3. Hooper, R. (2003, July 31). Alpine black swallowtail. The Japan Times. Retrieved from The Japan Times.

4. Kovner, A. (2015, November 3). The wild world of butterflies. Sierra. Retrieved from the Sierra Club.

5. LibreTexts. (2019). 11.2: Light energy and pigments. In LibreTexts Biology Library. Retrieved from LibreTexts.

6. Renoult, J. P., & Valeur, B. (2016, April 5). The colors of life. ChemViews Magazine. Retrieved from ChemistryViews.

7. Kinoshita, S., Yoshioka, S., & Miyazaki, J. (2008). Physics of structural colors. Reports on Progress in Physics, 71, 076401. Retrieved from IOPScience.

8. Bichell, R. E. (2014, November 12). How animals hacked the rainbow and got stumped on blue. Retrieved from NPR.

9. Morone, M. (2014, March 14). Brighter inks, without pigment: Nanostructured capsules could bring about paints and electronic displays that never fade. Retrieved from the Harvard School of Engineering.

10. Gibbs, J. P., Breisch, A. R., Ducey, P. K., Johnson, G., Behler, J., & Bothner, R. (2007). Chapter 7–Lizards and snakes: Species accounts [Smooth Greensnake (Smooth green snake)]. In The amphibians and reptiles of New York State: Identification, natural history, and conservation. Oxford University Press: New York. Retrieved from Google Books.

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