The bees and I have been battling yellowjackets, which are invading one hive and eating bees, honey, pollen, and larvae; when large numbers of yellowjackets have stormed the gates it is difficult for even a strong hive to recover.
That red stuff in the image below is propolis, which the bees make from tree sap. Honeybees use propolis to seal up the cracks in the hive, and it is an antibacterial. Humans have used propolis to treat infections and wounds since ancient times and recent studies show that it is resistant to MRSA.