Introduction 1960 2003 2005 2005 2006a 1998 2000 1954 2007 2007 Morpho 1972 1999 2002 2002 2003 2006 2006b Morpho 2006 Pieris rapae Knowledge of the spatial and spectral reflectance characteristics of single scales is essential to further develop our understanding of the coloration principles applied by butterflies. In the present study we investigate the scattering properties of wing scales of a variety of butterflies, and we correlate the scattering diagrams with the electron micrographs of the scale structure. We show that white scales of pierid butterflies are approximately random scatterers. Iridescent scales, with multilayer structures, exhibit directional reflection. Whereas some butterfly species appear to have scales with dominant iridescence, other species combine iridescence and scattering properties. Materials and methods  Animals  P. rapae Delias nigrina Morpho aega Colotis regina Urania fulgens Angular distribution of scattering by single scales 1 1 2 6 6 Fig. 1 a b  Fig. 2 a d Pieris rapae e h Delias nigrina i l Morpho aega m p Colotis regina q t Urania fulgens First column Bars Second column 1 black shadow upper part b f bright spot black hole ellipses b Third column 1 Fourth column  Spectrophotometry  2006b 1 Electron microscopy  4 4 6 Results P. rapae 2 1 2 P. rapae 1 2 2 2 2007 2 2004 2007 2007 2 2 D. nigrina P. rapae 2 2 2 M. aega 2 Morpho didius 1999 M. aega M. aega 2 2 2 2 1999 2002 2004 2 C. regina M. aega 2 2 2 2 2 2 2 U. fulgens 2 2 2 P. rapae D. nigrina C. regina 3 P. rapae D. nigrina C. regina D. nigrina 3 P. rapae 3 C. regina Fig. 3 P. rapae D. nigrina C. regina bold line P. rapae a D. nigrina b D. nigrina C. regina  Discussion 1999 2002 2002 3 Morpho 2006a C. regina 1972 2005 4 Gonepteryx rhamni 2007 4 2007 Fig. 4 Gonopteryx rhamni a Urania fulgens b closed arrows open arrow U. fulgens Bar  U. fulgens 2 4 2 4 2006b 2006 P. rapae Morpho 5 M. aega 5 5 5 2 5 6 6 Morpho Morpho Fig. 5 Morpho aega a bar b 2 bright white spot circles c bar d white spot  Fig. 6 5 X Y