The chemistry of the abdominal defensive secretions of six species of the rove beetle genus Bledius was examined. In all species the secretion contains the solid toxin p-toluquinone and its precursor p-toluhydroquinone dissolved in different solvents. In B. furcatus, B. tricornis and B. dissimilis these solvents are mainly alkenes and lactones, especially 1-undecene and γ-dodecalactone. In addition to alkenes and lactones the secretion contains decanoic acid and 3-methyl-2-butenoic acid in B. opacus and B. subterraneus. In B. arenarius the quinones are dissolved in octanoic acid and octyloctanoate, exclusively. In B. arenarius and B. opacus the secretion's content of p-toluquinone is reduced in comparison with the other species. Application experiments with the natural predators revealed that in B. arenarius this quinone reduction does not involve a reduction of irritation efficiency. This is probably due to the irriation properties of the B. arenarius solvent octanoic acid. The results are discussed with respect to the evolution of the different secretion types within the genus Bledius and within the subfamily Oxytelinae. |
