September 20, 2018
For beekeepers, smoke is one of their secret weapons for keeping bee stings to a minimum and has been for thousands of years, with some 2,500-year-old ancient Egyptian artwork depicting the practice. Despite how long smoke has been used to calm honey bees, however, it’s still unknown why it occurs—though some new research that was published in the Journal of Insect Science may give us an idea. Per their research, Dr. Stephanie Gage, with her colleagues from BetaTec Hop Products and the USDA’s Carl Hayden Bee Research Center, presented an analysis of smoke and how it affects defensive behavior in honey bees.
As part of this research, Gage and her team studied the “sting extension response” as well as two types of bee smoke—burlap, which beekeepers commonly use, and spent hop pellets, recycled materials made from used hop flowers. Sting extension responses, which occur when guard bees detect threats and extend their stingers, release alarm pheromones to alert the entire hive, mobilizing other worker bees to ready for attack and sting if the threat continues.
For the experiment, Dr. Gage provoked honey bees with mild electric shocks, saying, “We were looking for a repeatable way to ‘pester’ an individual bee that would be consistent among bees.” Gage’s team chilled the honey bees and immobilized them before using small Velcro straps to secure them onto a brass plate where the shocks were delivered. The plate of bees was set inside a chamber to be exposed to either no smoke, hops smoke, or burlap smoke, and then one shock was applied, and the behavior observed.
Surprisingly, the smoke didn’t affect the bees’ sting extension responses or their prior movements, but the smoke did affect a different behavior—venom droplet release. When responding to strong shocks, some bees extended stingers and released one venom droplet from their stinger tip. Per Gage, “The release of the venom droplet took us by surprise. We didn’t start out looking to record it. It became clear upon our first day of testing that some sting extensions released a venom droplet while others did not.” Gage’s team wrote the venom droplets were “more likely to be released with greater perturbation, and the probability of release was reduced with smoke.”
This response of venom release has previously been described, but there’s been very little debate of it in scientific literature. Gage’s team has hypothesized this venom droplet release is part of a bee’s defenses that amplifies its alarm pheromones, as the venom has a small amount of the pheromone and the droplets increase surface area. With this in mind, if the use of smoke decreases the likelihood of release, it also should decrease the colony’s overall defensiveness and the probability of beekeepers getting stung.
Despite what their research suggests, Gage’s team has cautioned that, outside a lab, bees rarely experience electric shocks. They’re hoping to evaluate the effects of smoke in the wild where bees can be more exposed to natural threats as well receiving cues from other bees. “We are still imagining the parameters of that experiment, but we will get there,” Gage said.
Photo By erika8213