If you've ever seen a dead bee that looks like it has partly exploded, there's a good chance it died a more NSFW death than you're picturing – it turns out that when drones die in extreme heat, their last act is to ejaculate out a part of their own abdomen.
"When drones die from shock, they spontaneously ejaculate," postdoctoral fellow at UBC's Michael Smith Laboratories and expert in bee health, Dr. Alison McAfee, said in a statement. "They have this elaborate endophallus that comes out and is about the size of their own abdomen. It's pretty extreme."
In a study examining bee die-offs during extreme heatwaves in British Columbia, McAfee and her team attempted to find ways of cooling hives to prevent them from – as the University of British Columbia puts it – "explosively ejaculating to death".
After one beekeeper got in touch with photos of dead drones during a 2021 heatwave, McAfee contacted others in the area and found they had witnessed similar large die-offs – particularly of their smaller starter colonies called "nucs". Some beekeepers saw up to half of their nucs dying off.
Usually focused on queen bees as a way of monitoring the environment, McAfee realized that die-offs of drones could be important too.
"We know that after six hours at 42 degrees, half of drones will die of heat stress," McAfee said. "The more sensitive ones start to perish at two, or three hours. That's a temperature they shouldn't normally experience, but we were seeing drones getting stressed to the point of death."
As well as deaths diminishing resources bees use to create new hives, fewer drones means less genetic diversity. This could lead to less resistance to disease and other problems.
During the heatwave studied, only 40 percent of queen bees successfully mated, compared with 75 to 80 percent mating success in better conditions. To prevent these problems, McAfee tested a few methods of cooling the hives while monitoring the temperature over the heatwave.
One method was to give the bees a kind of cooling station – a feeder full of sugar syrup.
"Bees will naturally go find water to bring back to the hive and fan it with their wings to cool down, which achieves evaporative cooling much like we do when we sweat," McAfee explained. "Giving them syrup nearby should let them do the same thing, and the sugar in it motivates them to take it down faster."
The other method, though less adorable, was more effective: putting styrofoam lids on the hives. Hives with cooling stations were 1.1°C (1.98°F) cooler than control hives, while those fitted with styrofoam lids were around 3.5°C (6.3°F) cooler than controls.
What's more, insulation from the styrofoam kept temperatures more stable, keeping the hive warmer at night and cooler during the daytime, so could be used to protect bees from the cold during winter – and from ejaculating themselves to death during the summer.