there are two strains of european corn borers that are defined by their sex pheromone communication variant. these are the "z" and "e" strains, named after the stereochemistry of the predominant isomer of 11-tetradecenyl acetate that they produce. the "e" variant of pheromone has a trans- configuration of hydrogen molecules around its double bond, while the "z" variant has a cis- configuration. the "z" strain produces a 97:3 ratio of "z" to "e" isomer pheromone while the "e" strain produces a 4:96 ratio of "z" to "e" isomer pheromone. a mixture of isomers is much more efficient in attracting the moth than a single component. the "z" and "e" strains can mate and produce intermediate variants.