The Douglas-fir cone moth, Barbara coljaxiana (Kearfott) (Lepidoptera: Tortricidae), has the capacity for prolonged diapause, i.e. diapause for two or more winters (Hedlin 1960). This diapause allows for temporal spacing of populations and reduction of intraspecific competition. Specifically, when cone crops are small, excessive moth densities can occur and cause conelet mortality prior to completion of feeding by cone moth larvae, which results in moth mortality. If all moths emerged each year, moth-caused destruction of the conelet population, particularly in years of light production, would have drastic effects on the moth population.