The sex pheromone components from the corn borer spreading widely in China,Ostrinia furnacalis Guenée, have been identified as (E)-and (Z)-12-tetradecenyl acetates (E andZ12-14∶ Ac). The ratio ofE isomer toZ isomer was 53 ∶ 47. Traps containing 1 × 10(-7)-1 × 10(-5) g of these compounds captured more males than did live females or their tip extract (3-6 female equivalents). Tetradecyl acetate (14 ∶ Ac) was also identified in the tip extract. Its quantity was about 1.8 times the sum of the other two isomers. However, including this compound in its natural ratio in pheromone traps resulted in a decrease in trap catches (P< 0.05).