Naturally grown photonic structures found in living organisms are among the most sophisticated devices that the human mind could imagine. One of the most remarkable consequences of these elaborate architectures is the so-called structural colours, which exhibit colour changes with viewing angle, i.e., iridescence. These colours play a vital role in the survival of living organisms such as insects, e.g., in the inter- and intraspecific recognitions. Furthermore, they are an inexhaustible source of inspiration for human invention, the so-called biomimetism and bioinspiration. For instance, bioinspired applications such as gas, temperature or pH sensors are currently under investigation. The photonic structures localised in scales on the cuticle (in particular, here, in a cavity) of the Brazilian Weevil Entimus imperialis are good examples showing various iridescent colours delivered by the interaction of light with these structures.