Matskási István (szerk.): A Magyar Természettudományi Múzeum évkönyve 99. (Budapest 2007)

Bálint, Zs., Horváth, Z. E. , Kertész, K. , Vértesy, Z. ; Biró, L. P.: Observations on scale structures and spectroscopic properties of Polyommatus lycaenid butterflies (Lepidoptera: Lycaenidae)

which the optical properties (refractive indices) change in a systematic way according to a three dimensional (3D), regular, or quasi-regular pattern. One of the most important functions for which 3D PBG materials are used in the natural world is signaling (PARKER 1998). Day flying Lepidoptera use PBG materials most frequently for colour generation: whilst monitoring or perching in their habitats male individuals of dorsally blue polyommatine lycaenid butterflies (Lepidoptera: Lycaenidae: Polyommatini), in common English name "the Blues", widely use their vivid blue wing colours generated by PBG materials built in the body of their wing scales for visual communication (LUNDGREN 1977). The Blues evolved special PBG materials in their dorsal wing scales, called Urania-type with "pepper-pot" structures (ELIOT 1973) (Figs 1-2). If these structures are missing from the body of the scales, the wing dorsa of the individuals are getting to be discoloured exposing the chemical colour (BIRÓ et al. 2003), which is brown due to melanin (BÁLINT & JOHNSON 1997) or carotene (BÁLINT, VÉRTESY & BlRÓ 2005). This phenomenon was termed as discolouration (BÁLINT & JOHNSON 1997). Figs 1-2. Scanning Electron Microscopy images showing Polyommatus genus group lycaenid scale micro- and nanostructures: 1 = blue colour generating cover scale of Polyommatus poseidon (HERRICH-SCHÄFFER, 1851) with pepper-pot structure, 2 = discoloured cover scale of Polyommatus admetus (ESPER, 1785) without pepper-pot structure In the case of brown dorsal polyommatine wings the melanin granulates are directly facing sunlight in the body of the scale and are able to absorb more energy than the blue coloured species (BlRÓ et al 2003). Discolouration results different thermal regulation in brown and in blue individuals. This change