The composition of stink bug allomones is similar for most species and includes hydrocarbons, as well as saturated and unsaturated aldehydes and esters. Analysis of extracts of the metathoracic glands of seven pentatomid species from different genera by gas chromatography/Fourier transform-infrared (GC/FT-IR) showed that the compound previously thought to be 1-tridecene actually showed characteristic bands of an internal as well as terminal double bond, the former compound having (Z)-configuration. The mass spectrum of an epoxy-derivative of the natural material demonstrated that the internal double bound was located at C4. GC/FT-IR and co-injections with synthetic standards on different capillary columns proved that all these stink bugs had 1-tridecene and (Z)-4-tridecene in their defensive secretions.