Methyl (2E,4Z)-decadienoate was isolated and identified as the major male-specific volatile ofEuschistus conspersus, E. tristigmus, E. servus, E. politus, andE. ictericus. In a sixth species,E. obscurus, this ester is a relatively minor male-specific component, with the major component being tentatively identified as methyl 2,6-dimethyltetradecanoate. Females, males, and nymphs ofE. conspersus, E. tristigmus, E. servus, andE. polituswere significantly attracted to methyl (2E,4Z)-decadienoate in field tests conducted in California and Maryland. Tests in Maryland also demonstrated that parasitic tachinid flies use theEuschistusunsaturated methyl-ester as a host-finding kairomone. It is not yet clear what role minor volatile components ofEuschistusplay in reproductive isolation.