Ingo Arndt / Inside wall of a natural Honey bee (Apis mellifera) hive inside a tree hole, propolis or bee glue visible, Germany.

Ingo Arndt / Propolis or 'bee glue' inside a Honey bee (Apis mellifera) hive in a tree hole, Germany.

Ingo Arndt / Chestnut bud (Aesculus hippocastanum), used by Honeybees (Apis mellifera) in making propolis or 'bee glue', Germany

Ingo Arndt / Honey bee (Apis mellifera) worker bees isolate wall inside their nest cavity, close to the entrance, with propolis or bee glue, Germany.