Division of Labor in Stingless Bee Nests: Does Each Kind of Propolis Have a Role?

Case studies of resin, beeswax, and propolis use by stingless bee colonies were made in four countries. Tetragonisca angustula has a central propolis deposit over the brood and consistently modifies resinous materials to make reddish brown, taffy-like propolis; its nest components (involucrum, brood cells, storage pots, pillars, propolis deposit) each appear distinct, but uniform across different geographic locations. The specific resin sources are unknown. Trigona fulviventris uses resin to build subterranean nests of hardened propolis. The bee is not a mutualist of Clusiaceae but forages aggressively to defend resin of Symphonia and Clusia from other bees. Clusia flowers, fruit, and post-seed dispersal fruit capsules are foraged, but Clusia rosea apparently does not require pollinators and is apomictic. Melipona panamica and Melipona fallax collect nest material and disperse seeds from Coussapoa panamensis (Urticaceae), a hemiepiphyte. Its seeds, within resinous fruit wax, are mixed in bee nest batumen and germinate there. Melipona nigrescens from the Andes lives alongside spectacled bears, a potential predator, and musters defending workers carrying bright yellow resin—an eye irritant. Cecropia bees, Plebeia (Nanoplebeia) spp. only nest in melittophytic Cecropia, surrounded by ant colonies, which they repel partly by biting. Collected resin provides a barrier ring at the nest entrance, forms a hard internal entrance tube, and is used to make external vent tubes of cerumen-beeswax. Beeswax in the Plebeia nests is taken from scale insects, Cryptostigma cecropiaphilum (Coccidae), contains carminic acid, and is sticky. Bees stockpile cerumen on brood cells. It was quickly removed to build a sheath after nest opening. All the above suggest aging, ripening, and modification of resin and other ingredients that make propolis, and the application of such non-food materials for specific functions.