A brood pheromone identified in honeybee larvae has primer and releaser pheromone effects on adult bees. Using gas chromatography-mass spectrometry (GC-MS) to evaluate fatty acid esters--the pheromonal compounds--in different parts of the larvae, we have localized the source of the esters as the larval salivary glands. A histochemical study describes the glands and confirms the presence of lipids in the glands. Epithelial cells of the gland likely secrete the fatty acids into the lumen of the gland. These results demonstrate the salivary glands to be a reservoir of esters, components of brood pheromone, in honeybee larvae.