Zenithoptera dragonflies are known for their remarkable bluish coloration on their wings and unique
male behavior of folding and unfolding their wings while perching. However, nothing is known about
the optical properties of such coloration and its structural and functional background. In this paper,
we aimed to study the relationship between the wing membrane ultra structure, surface micro structure
and color spectra of male wings in Zenithoptera lanei and test the hypothesis that coloration functions
as a signal in territorial fights between males. The results show that the specific wing colouration derives
from interference in alternating layers of melanized and unmelanized cuticle in the wing membrane,
combined with diffuse scattering in two different layers of wax crystals on the dorsal wing surface,
one lower layer of long filaments, and one upper layer of leaf-shaped crystals. The results also show that
the thicker wax coverage of the dorsal surface of the wings results in increased brightness and reduced
chroma. In the field experiments, we have demonstrated that there is a reduction of aggressive reactions
of rivals towards individuals with experimentally reduced amount of blue wing colouration.