A case of Blue Morpho Butterflies including, closest to us, Morpho rhetenor helena, largest on top Morpho menelaus, and smallest (pale blue) lower middle, Morpho sulkowski. Morpho wings have no blue pigment, and gain their iridescent colour by reflecting incident light repeatedly at successive layers leading to interference effects. The colours stay suprisingly true regardless of angle of view, probably due to highly uniform tetrahedral scale arrangements. Their underwings are brown with eye spots. Morphos are found in Central and South America. Their wings are used in jewelry and the butterflies are prized entomological and display specimens. Because they are not pigment based, their colours do not fade.