A comparative study of the chemical defensive system of tenebrionid beetles: Chemistry of the secretions

The chemical compositions of the defensive secretions of 147 species of tenebrionid beetles from 55 genera and 16 tribes were analysed by gas-liquid chromatography on three different stationary phases. All species contained toluquinone and ethylquinone, but benzoquinone was relatively rare. A great many species contained various 1-alkenes in addition to quinones. Species of Pedinini were distinguished by the secretion of n-propylquinone, whereas 2,3-methylmethoxyquinone set apart the subgenus Blapylis (of Eleodes) and possibly Amphidora. Large amounts of octanoic acid were restricted to the genera Embaphion and Neobaphion (both Eleodini), and small amounts of 1-nonadecene were restricted to Lariversius (Eleodini) and Cratidus (Amphidorini). Most species of Eleodes had complex secretions with toluquinone, ethylquinone, 1-nonene, 1-undecene, and 1-tridecene in various ratios. 1-Pentadecene and/or 1-heptadene occurred in substantial amounts in Tribolium, Uloma, Phaleria, Pyanisia, Melanopterus, Gonopus, Schelodontes, Psorodes, Neatus, and Merinus. The genus Argoporis (Scaurini) is unique in its synthesis of 6-alkyl-1,4-naphthoquinones, and other members of the tribe also contain characteristic, as yet unidentified compounds. Many groups not distinguished by unique compounds still show characteristic combinations and ratios of compounds, and these are discussed along with problems of variation at the individual, geographic, specific, and generic levels.