Honeybees collect antimicrobial plant resins from the environment and deposit them in their nests as propolis.

Honeybees produce propolis (also called bee glue) from resins that they collect from different plant organs and with which they mix beeswax. The term 'propolis' is of Greek origin: 'pro' meaning 'in front of/ for' and 'polis' meaning 'city' that is, in front (or for defence) of the city (Bankova et al. 2019). Propolis is used by bees as a building material in their hives, for blocking holes and cracks, repairing combs, and strengthening the thin borders of the comb (Ghisalberti 1979). A feral colony nesting in a tree cavity coats the entire inner walls with a thin (0.3 to 0.5 mm) layer of propolis forming what has been termed a 'propolis envelope' around the nest interior (Seeley and Morse 1976). Propolis is continually added to the nest walls during colony development and is first placed at areas prior to comb attachment, which not only creates a clean, smooth surface, but may also reinforce new comb (Seeley and Morse 1976; Visscher 1980). Propolis plays the role of chemical defence against microorganisms and as an embalmer of larger, dead intruders (insect, small animals) that have died in the hive and are too large to be removed by the bees (Ghisalberti 1979).

Propolis is not collected at all times of day, nor in all weathers. The mai