Conspicuous, bright colorations of insect compound eyes may be caused by two different mechanisms resulting in different functions: 1) A thin layer of bright, light scattering pigment inside the pigment cells bordering cornea and crystalline cones may determine the eye’s outer appearance when seen through the transparent dioptric apparatus. The insect’s vision is not influenced by this phenomenon (STAVENGA 1979). The cornea transmits light equally well for all wavelengths involved in vision. As examples Ischnura elegans VAN DER LINDEN (Odonata: Coenagrionidae) and Lathyrophthalmus aeneus (SCOPOLI) (Diptera: Syrphidae) are presented.
2) Interference filters in the cornea cause colorful, metallic reflections. Transmission measurements of single cornea lenses revealed that the interference filters act as color filters by reducing transmission of light in a small limited waveband. These filters influence vision, because they change the spectral composition of visual stimuli. Results of transmission measurements of cornea lenses of Heptatoma pellucens FABRICIUS (Diptera: Tabanidae) and Poecilobothrus nobilitatus LINNÉ (Diptera: Dolichopodidae) are given.