Defence of the city gates.
We guard trees with hollows provide animal homes. Hollow formation is a common trait in many Australian trees. At least 20% of bird species are hollow-dependent. All arboreal marsupials use tree hollows for shelter and breeding sites.
Honeybee and Tetragonula Carbonaria stingless bees both use tree hollows to nest. Inside these hollows bees line the cavity with propolis.
"Propolis" comes from the Greek language and means "in defense of" (pro) the city (polis)." The essential meaning is "defender of the city. Propolis is used to reinforce structural stability, provide thermal insulation and makes the hive stronger in defence.
Propolis is comprised of 50% tree resins, 30% beeswax, 10% essential aromatic oils, 5% pollen, 5% other organic compounds. The main active ingredients in propolis are flavonoids which the honeybees get from plant and flower.