Morphology of the Head Salivary and Intramandibular Glands of the Stingless BeePlebeia Emerina(Hymenoptera: Meliponini) Workers Associated with Propolis

Plebeia emerina (Friese) (Hymenoptera: Meliponini), like other stingless bees, collect large amounts of vegetal resin and store these materials, called propolis, in individualized clusters inside the nest that remain in a viscous state. The development of intramandibular and head salivary glands in P. emerina workers was studied in different life stages, aiming to relate gland functionality with the age in which they work at propolis maceration, biting the propolis clusters with the mandibles. The morphology of intramandibular and head salivary glands from newly emerged, 20–30 d old, and forager bees was analyzed. The greatest size of the head salivary glands occurred in 20–30-d-old worker bees, and the ultrastructure of this gland showed the presence of rough endoplasmic reticulum and lipid droplets. The intramandibular glands were of two types: glandular units (class 3 glands), present throughout the worker bee life span, and the secretory epithelium (class 1 glands), which hypertrophies in 20–30-d-old and forager bees. The development of the head salivary glands and the mandibular epithelium suggest that their products are added to the propolis clusters, supporting the hypothesis that they may serve in maintaining its viscous state.