Interference colors result from the reflection oflight from a series ofneighboring interfaces that are separated bydistances comparable with a quarter of the wavelength of light. .Interference colors are common in some adults of Lepidoptera insects. The integument layers producing interference are formed bymodifications ofthe scales. Each ofthe blue scales ofthe Morpho rhetenor butterfly, for instance, consists ofa flat basal plate carrying a large number ofnear-parallel vertically aligned ridges that run parallel with the length ofthe scale. Within each ridge are series ofhorizontal layers, separated byair spaces. Collectively, the horizontal layers in each adjacent ridge form a series of reflecting surfaces, which are spaced such that a blue color is produced by interference. Interference colors inother insects are produced byreflection atthe interfaces oflayers inthe cuticle which differ inrefractive index. Therefractive indices ofthe alternating layers inthe pupa ofthe danaid butterfly, Euploea mulciber, are 1.58 and 1.37. Injewel beetles, Chrysochroafulgidissima Buprestidae and tiger beetles, Cicindela japonica (Cicindellidae), these layers are inthe exocuticle, but in tortoise beetles (Cassidinae) and some butterfly pupae they are inthe endocuticle. Interference isresponsible for the iridescence ofthe membranous wings ofmany different insects, particularly Odonata.