When a colony is infected by pathogenic fungi, the bees bring to the hive greater amounts of propolis, a mixture of wax and plant resins with antifungal properties. These are the results of a study published in the journal PLos ONE .
“This behavior has evolved because the benefit of bringing the extra amount of resins to the hive outweighs the costs,” said Michael Simone-Finstrom, a researcher at the University of North Carolina (USA) and author of the study. “The colony knows that it is worth the effort,” he added.
The researchers found that, when a fungal treatment was applied to the hive, the bees carried up to 45 percent more propolis to the hive and, in addition, they removed the larvae parasitized by the fungi in a way that significantly reduced the infection. On the other hand, it seems that these hymenopterans can distinguish whether or not the fungi are pathogenic since, when applying innocuous fungi, the bees did not increase the transport of resins to the hive. But self-medication also has limits and, in the case of bees, bacterial infections did not cause an increase in propolis in the hive, despite the known antibiotic properties of this compound.
This work has practical implications in the world of beekeeping. For example, US beekeepers tend to prefer colonies with less resin. However, “we now know that this is a trait worth promoting as it offers bees a natural defense,” explained Simone-Finstrom.
