The butterfly of the year 2020 is …

endangered. That’s the sad truth, and a call for action.

It is the Green Hairstreak, and it was declared the butterfly of the year just then by the German ‘Bund für Naturschutz’ Foundation. It has certainly been my butterfly of the decade, because of its beautiful Gyroid nanostructure.

Its numbers are dwindling even though it’s not a fussy eater. This is an urgent reminder that we need to change our practices, in particular farming practices!

Here‘s the press release by the BUND: http://www.bund-nrw-naturschutzstiftung.de/schmetterlinge_des_jahres/schmetterling_des_jahres_2020_der_gruene_zipfelfalter/

Image by W. Schön (from BUND website)

In North-Rhine Westphalia (home of Borussia Dortmund and Schalke 04), numbers are now so low it’s considered an endangered species, and in some parts it has already disappeared.

For the physicists and materials scientists, and those that love beautiful structure, the Green Hairstreak features the amazing Single Gyroid Nanostructure, as we have now known for more than a decade. The green coloration is not from a pigment but from a photonic crystal … which, one could say, is largely a sophisticated version of the interference effects that we all know from oil films and soap bubbles.

The three-dimensional nanostructure of the Callophrys rubi (green hairstreak), known as the single gyroid: On the right in green is a 3D dataset obtained by electron tomography and on the left in blue is a mathematical model for that structure. (From Schröder-Turk et al, J Structural Biology, 2011)

Here are some of the publications that investigated the Single Gyroid structure in the Green Hairstreak and in other butterfly species:

B.D. Wilts, B. Apeleo Zubiri, M.A. Klatt, B. Butz, M.G. Fischer, S.T. Kelly, E. Spiecker, U. Steiner, G.E. Schröder-Turk, “Butterfly gyroid nanostructures as a time-frozen glimpse of intracellular membrane development“, Sci. Adv. 3, e1603119 (2017)

R.W. Corkery and E.C. Tyrode, “On the colour of wing scales in butterflies: iridescence and preferred orientation of single gyroid photonic crystals“, Interface Focus 7 (2017)

B. Winter, B. Butz, C. Dieker, G.E. Schröder-Turk, K. Mecke, E. Spieker, “Coexistence of both gyroid chiralities in individual butterfly wing scales of Callophrys rubi“, Proceedings of the National Academy of Sciences 112(42), 12911-12916 (2015)

M. Saba, B.D. Wilts, J. Hielscher and G.E. Schröder-Turk, “Absence of circular polarization in reflections of butterfly wing scales with chiral Gyroid structure”, Materials Today: Proceedings 1, 193-208 (2014)

S. Yoshioka, B. Matsuhana and H. Fujita, “Polarization-dependent Tessellated Pattern of the Wing Scale of the Parides Sesostris Butterfly“, Materials Today Proceeding, 2014

G.E. Schröder-Turk, S. Wickham, H. Averdunk, F. Brink, J. Fitz-Gerald, L. Poladian, M.C. Large and S.T. Hyde, “The chiral structure of porous chitin within the wing-scales of Callophrys rubi”, J. Struct. Biol. 174, 290-295 (2011)

V. Saranathan, C.O. Osuji, S.G. J. Mochrie, H. Noh, S. Narayanan, A. Sandy, E.R. Dufresne, and R.O. Prum, “Structure, function, and self-assembly of single network gyroid (I4132) photonic crystals in butterfly wing scales“, PNAS 107 (26) 11676-11681 (2010)

K. Michielsen and D. Stavenga, “Gyroid cuticular structures in butterfly wing scales: biological photonic crystals“, Journal of the Royal Society Interface 5, 2007

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