The rate and periodicity of the emission of the sex pheromone [(Z)-11-hexadecenal] from the pheromone glands of individual female artichoke plume moths,Platyptilia carduidactyla,were quantified. The mean rate of volatilization of (Z)-11-hexadecenal from the glands of the moths peaked at 1.52 ± 0.41 (SE) ng/min during the scotophase, and was at low levels during the entire photophase. This periodicity in emission rate paralleled the behavioral periodicity of calling by females, indicating a close coordination of the biochemical and behavioral aspects of pheromone release. The highest recorded emission rate from a femaleP. carduidactylawas 5.1 ng/min. No other pheromone-like compounds were detected in these pheromone collections.