Wing scales of maleE. mulciberandT. aeacusbutterflies have
been investigated by SEM and optical reflectance measurement.
Blue backgrounds of theE. mulciber’s forewing have brown scales.
It has been elucidated that a highly tilted, triple-layered arrangement in these scales produces a violet-green iridescence in a wavelength range from 380 to510 nm due to multiple interference
from the cuticle-air layers. Besides the dark zone where no reflection geometrically occurs, human invisible zones due to ultraviolet
reflection appear so that the visible reflection is limited within an
angle range of 10.5–119.5. No iridescence in dark brown area in
the hindwing indicates that the double-layer arrangement is not
enough to reflect observable interference light. The patch between
the 7 and 4 veins in the hindwing is covered with strange scales,
which have a form of flat fibre as long as several hundredlm, hav