Abalg / Wikipedia, Tiny Fox Lab

Propolis or bee glue is a resinous mixture that honey bees produce by mixing saliva and beeswax with exudate gathered from tree buds, sap flows, or other botanical sources.

It is used as a sealant for unwanted open spaces in the hive.

Propolis is used for small gaps, while larger spaces are usually filled with beeswax. – Tiny Fox Lab

Preview photo credit: Abalg / Wikipedia
Source: https://en.wikipedia.org/wiki/Propolis