The Diversity of Chemicals of the Defensive Secretions of Five Pterostichine Ground Beetle Species (Coleoptera: Carabidae) and the Morphology of Their Pygidial Glands

The defensive substances of ground beetles are synthesised and stored in a pair of defensive glands, commonly referred to as abdominal or pygidial glands. The chemical composition of the pygidial gland secretions and the morphology of the glands were studied in adults of four species belonging to the tribe Pterostichini: Poecilus cupreus Linnaeus, 1758, Pterostichus melanarius Illiger, 1798, P. anthracinus Illiger, 1798, and Stomis pumicatus Panzer, 1796. In addition, Tapinopterus cognatus (Dejean, 1831) was examined only with regard to the chemistry of its secretion. The pygidial gland secretions of the five species were investigated using gas chromatography-mass spectrometry (GC-MS). The combined presence of methacrylic acid and tiglic acid was observed in all taxa studied. 2-Tridecanone, which was detected in all species except P. cupreus, is reported for the first time in the defensive secretions of representatives of Pterostichini. The pygidial glands of the first four species were examined using both bright-field microscopy (BFM) and nonlinear microscopy (NLM). The examined species were similar in the general appearance of the glands, with the greatest differences observed in S. pumicatus.