In a previous entry I have pointed out the biophotonic possibilities in butterfly wings. A recent article in the Journal of Experimental Biology provides an extensive survey of wing scale optical properties. There had been no less than four different methods proposed by which butterfly wing scales could reflect colored light, this study found that only one method is at work.

The … analyses … of colour producing butterfly scales document that all species are appropriately nanostructured to produce visible colours by coherent scattering, i.e. differential interference and reinforcement of scattered, visible wavelengths.

They also found that the blue pigment of one Papilio species is not an incoherent Tyndal scattering phenomenon but rather the result of a fluorescent blue pigment. The take home message is that whether the nanostructuring is external or internal the method of filtering is the same.

JEB Abstract