Pteridines are important cofactors for many biological functions of all living organisms, and they were first discovered as pigments of insects, mainly in butterfly wings and the eye and body colors of insects. Most of the information on their structures and biosynthesis has been obtained from studies with the model insects Drosophila melanogaster and the silkworm Bombyx mori . This review discusses, and integrates into one metabolic pathway, the different branches which lead to the synthesis of the red pigments "drosopterins", the yellow pigments sepiapterin and sepialumazine, the orange pigment erythropterin and its related yellow metabolites (xanthopterin and 7-methyl-xanthopterin), the colorless compounds with violet fluorescence (isoxanthopterin and isoxantholumazine), and the branch leading to tetrahydrobiopterin, the essential cofactor for the synthesis of aromatic amino acids and biogenic amines.