Iridescence and Butterflies

Male Varied Eggfly - each wing at different angle to light source to demonstrate  iridescence

The first rains of the wet season have been and gone. The predicted follow up rains have not eventuated.
A few afternoons a week clouds build above the 40C+ heat on the plains, blacken and sweep around the horizon scattering lightning displays in their wake. Occasionally a storm erupts above us and wind swirls rain around the town.

Underwings of male Varied Eggfly 

Beside our house is a concrete-floored, iron-roofed structure. It is open on all four sides, in the dry season to hot winds and flying dust, in the wet season to wind and rain.  It provides shelter on hot afternoons to all manner of creatures.

Over the past few weeks every time I walk into the covered area a male Varied Eggfly butterfly almost crashes into me.  The iridescent blue flickering from his upper wings is visually confusing, stopping me in my tracks before it flutters away. 
These Eggflies take up residence around our yard after the first rains. Their numbers fluctuate with changing weather conditions yet they persist almost throughout the year.
On the hottest days a male perches upside down on the gutter just above where I enter the area. He slowly opens and closes his wings, rocking  his body forward and backward in concert with his wing movement. Perhaps this is a cooling method. I have seen females doing the same thing.
After a few encounters with this male I began to wonder if they really were accidental. The male is supposed to be a territorial animal.
The male is about seven and a half centimetres from wing tip to wing tip. The female a centimetre or so wider.
 Eggflies are spectacular creatures. The female is rich brown with burnt orange and white markings. She is more ornate than the male but lacks his iridescence.

Female Varied Eggfly

Iridescence in butterflies is an entrancing quality and has engaged the interest of scientists since Aristotle. Iridescence on a butterfly's wing occurs because of interference when light interacts at the boundary of two pigmented colours with highly contrasting refractive indices. This and diffraction from the wing scales produce iridescence when seen from certain angles. The male Varied Eggfly's upper wing is a velvety black with white splashes. Blue iridescence is seen fron certain angles around the boundary of the two colours.
I often see a male Eggfly seemingly "leading" a female into his territory, his wings flickering blue light in the sunshine. So I suppose the theory that particular iridescence is a mating signal in certain butterflies is true. The other theory, that iridesence can be a predator deterrent may also be true as I have not so far seen any of the numerous insectivorous birds around here hunting an Eggfly.