Morphological Features of the Pygidial Glands and Chemical Composition of Their Secretions in Three Ground Beetle Taxa of the Tribe Chlaeniini (Coleoptera: Carabidae)

Abstract

The relationship between the morphology of pygidial glands and the chemical nature of their secretions in the tribe Chlaeniini (family Carabidae) has long been recognised. We analysed the morphological features of the pygidial glands and the chemical composition of their secretions in three taxa: Chlaenius (Chlaeniellus) tristis (Schaller, 1783), C. (Chlaenites) spoliatus spoliatus (Rossi, 1792), and C. (Chlaenius) festivus festivus (Panzer, 1796). We examined the morphology of the pygidial glands in all three taxa using bright-field microscopy (BFM) and nonlinear microscopy (NLM). We used gas chromatography–mass spectrometry (GC–MS) and nuclear magnetic resonance (NMR) to analyse the chemical composition of the secretions. We measured and photographed the glands and conducted comparative morphological analyses. We detected a total of 21 chemicals in the pygidial gland secretions of the studied Chlaeniini. We found the highest number of compounds in C. tristis (17), slightly fewer in C. festivus festivus (13), and the lowest number in C. spoliatus spoliatus (seven). Thirteen compounds were new to the tribe Chlaeniini, eight of which were also new to the entire family Carabidae. The most dominant compound in the secretions of all three taxa was 3-methylphenol. We also discussed the taxonomic value of the chemical composition of the pygidial gland secretions.