Seasonal benefits of a natural propolis envelope to honey bee immunity and colony health.

Honey bees, as social insects, rely on collective behavioral defenses that produce a colony-level immune phenotype, or social immunity, which in turn impacts the immune response of individuals. One behavioral defense is the collection and deposition of antimicrobial plant resins, or propolis, in the nest. We tested the effect of a naturally constructed propolis envelope within standard beekeeping equipment on the pathogen and parasite load of large field colonies, and on immune system activity, virus and storage protein levels of individual bees over the course of a year. The main effect of the propolis envelope was a decreased and more uniform baseline expression of immune genes in bees during summer and autumn months each year, compared with the immune activity in bees with no propolis envelope in the colony. The most important function of the propolis envelope may be to modulate costly immune system activity. As no differences were found in levels of bacteria, pathogens and parasites between the treatment groups, the propolis envelope may act directly on the immune system, reducing the bees' need to activate the physiologically costly production of humoral immune responses. Colonies with a natural propolis envelope had increased colony strength and vitellogenin levels after surviving the winter in one of the two years of the study, despite the fact that the biological activity of the propolis diminished over the winter. A natural propolis envelope acts as an important antimicrobial layer enshrouding the colony, benefiting individual immunity and ultimately colony health.

Handling sticky resin by Stingless Bees: adhesive properties of surface structures.

Many Stingless Bees (Hymenoptera: Meliponini) like Tetragonisca angustula collect resin to defend their nests against intruders like ants or Robber Bees. Small portions of resin are attached to intruders bodies and extremities causing their immobilization. It has been observed that resin is removed easily from the bee's mandible but adheres strongly to the intruder's cuticle. We tested the hypothesis that resin sticks lesser to the mandibles of Stingless Bees than to the surface of intruders due to special surface structures or adhesive properties of these structures. The surface structures of the mandible of T. angustula and the trochanter of Camponotus sericeiventris were studied by scanning electron microscopy. To measure adhesion properties, selected surfaces were fixed on a fine glass pin and withdrawn from a glass tip covered with resin. The deformation of the glass pin indicates adhesion forces operating between the resin and the selective surface. The absolute value of the forces is computed from the glass pin's stiffness. It has been shown that resin sticks more to the smooth mandible of the bee than to the structured trochanter of the ant. A new hypothesis to be tested says that the bees might lubricate their mandibles with nectar or honey to reduce the resin's adhesion temporarily.

[Organoleptic and physicochemical characteristics of propolis in the Province Of Nuble, VIII Region-Chile]. / Características organolépticas y físico-químicas de propóleos de la Provincia De Nuble, VIII Región-Chile.

Propolis ("bee-glue") is a gummy resinous substance elaborated by honey bees (Apis mellifera) from different types of plant resins. The chemical composition of propolis is very complex and variable as it depends on the botanical source and the environmental conditions prevailing at the location where the resin is collected by bees. The objective [corrected] of this study was to determine the propolis organoleptic and physicochemical properties of different types in the Province of Nuble (VIII Región, Chile). Samples were collected at different sites located in the Central Valley, ranging from the coast to the mountain skirts. Analyses included humidity, ashes, wax content, total phenolics content, total flavonoids, mechanical impurities, oxidation time, and solubility in ethanol. Results showed that propolis extracts from coastal sites are better quality than those collected at mountain skirts, and these in turn are better than propolis obtained from the Central Valley. All propolis analyzed in this study can be classified according to the Brazilian norm as high flavonoid content. The same homogeneity is observed in the amounts of total phenolics found in the samples. In general terms, properties of the propolis samples analyzed fulfill the quality requirements of the current international standards.