Honeybees, those good little workers, will do whatever it takes to protect their hive, including the ultimate sacrifice.
We've known for some time that Japanese honeybees (Apis cerana japonica) form what's referred to as a "hot defensive bee ball" around would-be invaders, particularly the Japanese giant hornet (Vespa mandarinia japonica), and for good reason. These hornets can kill almost 40 honeybees in a minute, and their tough exteriors render the bees' stingers useless. As the video above shows, the bees have developed another method of attack: They surround the would-be attackers and produce heat that reaches up to 115 degrees Fahrenheit (45 degrees Celsius). The heat basically means death for the hornet.
But it also means a reduced a lifespan for the bees that form the "hot defensive bee ball." According to a study published in Behavioral Ecology and Sociobiology, Japanese honeybees that participate in the bee ball have a significantly shortened lifespan compared to other bees in the hive. In a lab setting, researchers took bees between 15 to 20 days old and exposed them to an attack. The bees that formed the bee ball were dead within 10 days after the attack while those that didn't participate and were kept in a hive at 90 F, were dead within 16 days. (To put this into perspective, honeybees only live for a few weeks.)
Researchers also exposed the laboratory hive to multiple attacks — something that would also happen in the wild — and found that the bees that participated in the first bee ball were more likely to participate in a second. Researchers aren't sure why the bees engage in this sort of self-sacrifice, but suspect it could be a way of keeping the colony's population somewhat stable. Otherwise, there would be a complete loss of the worker population if news bees participated every time.