MEDIA RELEASE — MAY 15, 2026 — R0043
At the first hint of the weather warming, male eastern carpenter bees spring into action. A territorial lot determined to mate, they gather near the entrances of nests — where combat then begins.
“They hover near a female, sometimes guarding her closely,” says Lyllian Corbin (BSc ’19), a Brock University Biological Sciences PhD candidate. “The males beat each other up all day, chase each other around, get into fights, bite, form into a ball and then break apart and come back together. So, it gets pretty chaotic.”
Fascinated by these and other behaviours, Corbin designed an experiment to identify the internal mechanisms behind the territorial behaviour.
Now, the results are in.
Just in time for World Bee Day on May 20, Corbin presented her research findings at the Canadian Society for Ecology and Evolution’s Annual Conference in her talk, “Investigating Juvenile Hormone Effects on Aggression and Seasonal Flight Timing in Male Eastern Carpenter Bees.”
She found that juvenile hormone — which regulates development in immature insects and plays a role in reproduction — was fuelling the aggression.
During her experiment, Corbin used a clear, circular tube to observe how male bees interact with one another and measured how long it took before they displayed aggressive behaviour towards one another.
Corbin then applied methoprene, a substance mimicking the juvenile hormone, to the bees’ abdomens in one treatment group while a second group went without.
She found most bees treated with methoprene became aggressive more quickly.
“We had some knowledge on how this hormone influences females but not males,” Corbin says. “There is still a lot to learn about the factors that influence male territoriality in these bees. Now, we have more insight on how hormones enable males to defend their territories.”
Corbin also set out to determine if the concentration of juvenile hormone in male bees fluctuates during the season.
She captured male carpenter bees before and after females flew out of their nests and compared the levels of juvenile hormone in their hemolymph — a fluid similar to blood.
Corbin found juvenile hormone levels were higher in males caught before the females flew out of their nests, which she says shows males probably have to become aggressive quickly if they want to start establishing their territory with competitors nearby.
During her fieldwork, however, Corbin noticed a group of male bees who appeared to be hovering in their territories later in the spring season than she expected. Their juvenile hormone levels were high.
“I think one of the reasons for that is that juvenile hormone acts as an internal motivator for the males to keep going,” Corbin says. “They experience a lot of stress outdoors with being exposed to the sun, with the heat. They’re beating each other up and injuring themselves all the time, they’re using their flight muscles all day.”
Her supervisor, Professor of Biological Sciences Miriam Richards, says Corbin’s research sheds more light on juvenile hormone, which is a major regulator of juvenile development that is repurposed in adulthood with different functions.
“Lyllian’s research shows how hormones can have completely different roles at different stages and in different sexes,” says Richards. “It’s a fun example of how evolution makes many different products out of the same building blocks.”
Richards heads up Brock University’s Bee Lab, which studies the behaviour, evolution and ecology of bees in the Niagara region and beyond.
For more information or for assistance arranging interviews:
*Maryanne St. Denis, Associate Director, Strategic Communications, Brock University, [email protected] or 905-246-0256
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