The defensive secretion of Eurycantha calcarata (Phasmida: Lonchodidae) - chemical composition and method of collection

Chemical defence in insects is an increasingly popular subject of research and has the potential for providing unexplored compounds with unknown properties for drug and repellent discovery, so the secretions of various species of insects are currently being studied, and new ways of collecting these secretions are being sought. Silica gel and activated carbon were used as absorbents to collect the sprayed defensive secretion of Eurycantha calcarata. Using gas chromatography coupled with mass spectrometry, 49 compounds were identified, including 19 carboxylic acids, nine esters, ten alcohols, five hydrocarbons, and other organic compounds. The most abundant two compounds from each group were: hexadecanoic acid, octadecanoic acid, 9-hexadecenoic acid octadecyl ester, hexadecanoic acid tetradecyl ester, octacosanol, triacontanol, tridecane, and tetradecane. Silica gel turned out to be a better absorbent because it captured more compounds than the activated carbon. The mass of the absorbent did not affect the quality of the analyses. This paper is the first describing the volatile secretions emitted by phasmid representatives that originate from abdominal structures rather than the glands on prothorax. The presented results of the analyses and the known properties of the detected compounds give grounds for the conclusion that these secretions are of importance for defence in this species of phasmid.