Six novel keto carotenoids have been isolated from the stick insect. The structure of the predominant red pigment has been assigned to 3,4,3′,4′-tetradehydro-β,β-carotene-2,2′-dione on the basis of electronic, infrared, and mass spectra. Minor pigments are 3,4-didehydro-β,β-carotene-2,2′-dione, 2′-hydroxy-3,4-didehydro-β,β-caroten-2-one, and 2′-hydroxy-β,β-caroten-2-one. Two other compounds, β,β-caroten-2-one and β,β carotene-2,2′-dione, have been tentatively identified. The ad ditional occurrence of β,β-caroten-2-ol and β,β-carotene-2,2′-diol has been reported recently. All hydroxylated pigments are mainly present as fatty-acid esters. During hydride reduction of the 3,4-didehydro-2-one compounds hydrogenation of the 3,4-double bond was observed as a side reaction. A hypothetical scheme of carotenoid metabolism in the stick insect is proposed. According to this pathway the keto groups are introduced by a pseudo one-step reaction; the hydroxylated pigments are thought to be reduction products of the corresponding ketones. The proposed pathway is fitting more to physiological data than an alternative one based on the hydroxyl →carbonyl sequence.