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.
-Stingless bees collect plant resins and make it into propolis, although they have a wider range of use for this material than do honey bees (Apis spp.). Plebeia spp. workers employ propolis mixed with wax (cerumen) for constructing and sealing nest structures, while they use viscous (sticky) propolis for defense by applying it onto their enemies. Isolated viscous propolis deposits are permanently maintained at the interior of their colonies, as also seen in other Meliponini species. Newly-emerged Plebeia emerina (Friese) workers were observed stuck to and unable to escape these viscous propolis stores. We examined the division of labor involved in propolis manipulation, by observing marked bees of known age in four colonies of P. emerina from southern Brazil. Activities on brood combs, the nest involucrum and food pots were observed from the first day of life of the marked bees. However, work on viscous propolis deposits did not begin until the 13 th day of age and continued until the 56 th day (maximum lifespan in our sample). Although worker bees begin to manipulate cerumen early, they seem to be unable to handle viscous propolis till they become older.
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