Headspace gas chromatography-mass spectrometry: a fast approach to the identification and determination of 2-alkyl-3-methoxypyrazine pheromones in ladybugs

Static headspace sampling technique coupled with gas chromatography and mass spectrometry was used to investigate the presence of volatile 2-alkyl-3-methoxypyrazines in three different species of ladybugs of the Coccinellidae family. The species investigated were Coccinella septempunctata, Harmonia axyridis and Hippodemia convergens. 2-isopropyl-3-methoxypyrazine (IPMP) was identified in all three species with detectable levels of 2-sec-butyl-3-methoxypyrazine ( SBMP) and 3-isobutyl-2-methoxypyrazines (IBMP) in only Hippodemia convergens and Harmonia axyridis species. Relative amounts of 2-alkyl-3-methoxypyrazines based on body mass showed that Hippodemia convergens had the highest levels of all three methoxypyrazines and Coccinella septempunctata the least.