Two-dimensional structures are rather rare in arthropods (Fig. 10.1). They are most often one-dimensional structures of the multilayer type, modulated by folds or cells on a much larger scale, so that the latter do not generate perceptible diffractive effects (Fig. 10.2). We find real 2D structures in a few families of Lepidoptera, including the Morphidae, which we will detail here. It looks like a network of striae, like what we presented in the previous chapter, but this time each stria is made up of a stack of thin layers: the lamellae. The multilayer generates interference in the blue and the striae act as a selective reflection grating which diffracts these waves in different directions (Fig. 10.3).