This is a photo of a purple mountain swallowtail butterfly (Graphium weiskei) from Papua New Guinea, showing the rows of overlapping scales that cover the underside of the hindwing and the hollow rib-like veins that are distributed across it. The backlighting highlights the blue color (on the left side of the image) and gives the scales here somewhat of an ethereal look. The blue, green, and purple colors on this butterfly are not produced by the scales on the wing, but rather pigments within the wing membrane (1, 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: 45


Moths and butterflies are members of the scientific order Lepidoptera–a Greek term that translates to “scale wings” (lepidos=scale, ptera=wings)(3). The order contains around 15,000 species of butterflies and 160,000 species of moths (5). (Lepidopterans apparently account for nearly 20% of all known insects (3)!) Butterflies have a pair of forewings and a pair of hindwings (4). Generally, the wings are composed of a membrane made of chitin, which is interspersed with tubular “veins” and covered on both sides with scales (5). The color of the scales is oftentimes used to attract mates, to repulse predators, and/or for camouflage (5). The overlapping arrangement of the scales across the wing increases the butterfly’s thrust and lift, helping it conserve the energy it needs for flight (6). Scales can also absorb heat and serve as an insulator (7, 9). The veins provide flexibility and rigidity to the wing, transport blood, and are a passageway for both nerves and the tubes (tracheae) used for breathing (5, 7, 8, 9). Butterfly “blood,” called hemolymph, is pumped by a tube shaped “heart” in the body and small organs at the bases of the wings (10). It carries nutrients, waste, hormones, and other materials (11). The tracheae are tiny air tubes. Air enters the butterfly through holes, called spiracles, in the thorax and abdomen and travels via the tracheae through the wings, delivering oxygen directly to the tissues (9).


1. Barbier, M. (1983). The pigments of Papilio graphium weiskei: Sarpedobilin and ommin responsible for a unique pattern in a butterfly wing membrane [Abstract]. Comparative Biochemistry and Physiology Part B: Comparative Biochemistry, 76(1). Retrieved from Science Direct.

2. Clarke, K. (2013, April 11). Graphium weiskei butterfly skeleton [blog]. Retrieved from Bug Under Glass.

3. Scudder, G.G.E. & Cannings, R.A. (2007). Order Lepidoptera (moths & butterflies): Key and description of families. In Lepidoptera and associated orders of British Columbia. Retrieved from The University of British Columbia’s Department of Zoology.

4. Opler, P. A. (1998). A field guide to Eastern butterflies. Peterson Field Guides. New York: Houghton Mifflin Company. Retrieved from Google Books.

5. Silver, J., Fern, G. R., & Ireland, T. G. (2015). Materials Suitable for preparing Inorganic nanocasts of butterflies and other insects. Journal of Physics: Conference Series, 619. Retrieved from IOPScience.

6. Slegers, N., Heilman, M., Cranford, J., Lang, A., Yoder, J., & Habegger, M. L. (2017). Beneficial aerodynamic effect of wing scales on the climbing flight of butterflies [Abstract]. Bioinspiration & Biomimetics, 12(1). Retrieved from IOPScience.

7. Patil, S. & Magdum, S. (2017). Insight into wing venation in butterflies belonging to families Papilionidae, Nymphalidae and Pieridae from Dang Dist Gujarat, India. Journal of Entomology and Zoology Studies, 5(3), pp. 1596-1607. Retrieved from ResearchGate.

8. Oberhauser, K. (2013). Answers from the Monarch butterfly expert: Spring 2013. Retrieved from the Journey North program.

9. Scott, J. A. (1992). The butterflies of North America: A natural history and field guide. Stanford, CA: Stanford University Press. Retrieved from Google Books.

10. Otto, H. (2014). Butterflies of the Kruger National Park and surrounds. South Africa: Penguin Random House. Retrieved from Google Books.

11. Kanost, M. R. (2009). Chapter 117: Hemolymph [Publisher summary]. In Encyclopedia of Insects (Second Edition). Retrieved from ScienceDirect.

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