the present invention provides a sustained release pheromone formation comprising the sex pheromone substance which is an aldehyde compound wherein the formation can prevent the degradataion of the aldehyde compound and release the compound at an uniformed rate during the control term of the subjective pest insects . the sustained release pheromone formation is obtained by mixing an aliphatic derivative of which number of carbon atoms is equal to or less than that of the sex pheromone substance with a c 10 - 18 aldehyde which is a sex pheromone and then filling the resulting liquid mixture in a plastic container .