2-Heptanol, 2-alkanones (C7 and C9) and 3-hydroxyalkanoic acids (C8 and C10) were identified in worker mandibular glands, or in worker head extract of stingless bees, bumble bees and honey bees. 2-Heptanol is reported to be an alarm pheromone in stingless bees. 2-Heptanone is regarded as one of alarm pheromones in Apis species. Application of deuterated 3-hydroxyalkanoic acids onto mandibular glands of honey bees and bumble bees resulted in detection of deuterated 2-alkanones. Thus, 2-alkanones are biosynthesized through oxidative decarboxylation from corresponding 3-hydroxyalkanoic acids in the mandibular glands. Distribution of 2-alkanol, 2-alkanone, 3-hydroxyalkanoic acid in social hymenopterans and structural relations in these chemicals will be presented.