Sticky secretion from two pairs of defensive glands of rove beetleDeleaster dichrous (Grav.) (Coleoptera: Staphylinidae) : Gland morphology, chemical constituents, defensive functions, and chemotaxonomy

Abstract

The phylogenetically primitive rove beetleDeleaster dichrous (Grav.) (Oxytelinae) has been shown for the first time to possess two pairs of neighboring abdominal glands which are depleted simultaneously on molestation. The morphology of these glands is described. The defensive constituents of theDeleaster glands were elucidated directly from the mixtures by gas chromatographic-mass spectroscopic methods and microchemical reactions. The paired whitish glands secrete iridodial, which polymerizes on exposure to air to form an adhesive that probably deters small predatory arthropods. The red gland system ofD. dichrous contains the toxicp-toluquinone and a variety of isopropyl andsec-butyl esters. Artificial quinoid ester mixtures simulating the secretion ofD. dichrous showed only weak effects on mortality ofLucilia larvae in comparison with more effective secretions of phyiogenetically derived Oxytelinae. The secretion of the primitive genusDeleaster is characterized chemotaxonomically by β, γ-unsaturated C12 acids and esters, which are postulated as precursors for the characteristic defensive compounds of the derived species, thus indicating a clear evolutionary trend at the micromolecular level.