Propolis is one of four substances, along with nectar pollen, and water, that foraging honey bees bring into their hive. The collection of propolis is an important colony protection behavior. Bees collect propolis from the sap, gums, and resins of trees, often evergreens. The sticky substance is used to seal cracks and small openings in the honey bee colony’s hive. It is the “bee glue” that attaches beeswax combs to the hive. When a swarm of bees moves into a hollow tree cavity, or when a beekeeper hives a colony in a new hive, the bees varnish the inside walls of their new home with propolis. Not only does the propolis provide a protective barrier against drafts and moisture, it also provides antimicrobial protections. Foraging bees returning to their hive walk across an antibacterial and antifungal “door mat” of propolis deposited at the hive entrance. Honey bees use propolis to help protect the colony from invaders. Bees entomb with propolis dead mice or intruding insects too large to drag from the hive, preventing the spread through the hive of bacteria from decaying pests. Bees also trap Small Hive Beetles in propolis “jails” within the hive.
The behavior of collecting propolis is a heritable trait. Some beekeepers in the past considered manipulating heavily propolized hives unnecessarily messy, and therefore selected for bees that collected little propolis. However, colony health benefits of having plenty of propolis in the hives makes it advantageous to encourage propolis collection. An article published in the Journal of Economic Entomology, https://entomologytoday.org/2018/11/28/propolis-how-beekeepers-encourage-better-hive-health/, describes how researchers tested several means of roughening the interior of bee hives to encourage bees to fill small openings with propolis. I regularly roughen new hive boxes with a steel brush and a jagged flint rock from Arkansas’ Boston Mountains. Researcher Dr. Keith Delaplane, entomology professor at the University of Georgia, describes encouraging bees to deposit extra propolis as partnering with biology. In today’s photo bees eagerly gather and reuse propolis from a recently opened hive.--Richard