3-Methyl-1-(methylthio)-2-butene: a component in the foul-smelling defensive secretion of two Ceroglossus species (Coleoptera: Carabidae)

A sulfur-containing compound causes the foul smell of the defensive pygidial gland fluid of Ceroglossus buqueti Laporte and Ceroglossus magellanicus Gehin. This compound was identified as 3-methyl-1-(methylthio)-2-butene by a comparison of its mass spectrum, and chromatographic properties with those of a chemically synthesized standard. Although a few sulfur compounds are known from insect secretions, this sulfur-bearing isoprene derivative has not been characterized previously from any arthropod source. Additional components in the defensive section include acetic, propanoic, isobutyric, butanoic, methacrylic, ethacrylic, tiglic and benzoic acids, and 11-tricosene. Samples prepared from specimens of Ceroglossus chilensis Eschscholtz showed methacrylic, ethacrylic, and other acids. However, 3-methyl-1-(methylthio)-2-butene was not detected in the defensive fluid of C. chilensis.