Male carpenter bees have a reputation for being aggressive, especially when they dive-bomb those who venture too close to nests they’re guarding.

Lyllian Corbin (BSc ’19), a Brock University Biological Sciences PhD student, is fascinated with watching male carpenter bees in action and hopes to draw attention to the crucial pollinators as World Bee Day approaches on Monday, May 20.

In the spring, they emerge from their nests before the females and establish territories near the nest entrances to protect or pursue those females. They guard their territories by hovering and chasing, or even fighting, other bees that pose a risk.

Corbin’s interest in studying the role of hormones in aggression is not just academic. Bees play a critical role in the pollination of food crops and other plants around the world.

She is creating a two-fold experiment to study the way male carpenter bees interact with one another and whether hormones influence their behaviour.

As part of the project, she will set up tests to evaluate a pair of male bees within a circular tube, either in the lab or in the shade outdoors. By completing the testing in tubes, Corbin is better able to observe the bees’ interactions with one another compared to tracking them while they fly in open spaces.

The tubes also replicate the carpenter bees’ natural environment, as they nest in tunnels they have burrowed into wood. This creates a neutral setting for males to interact undisturbed by their surroundings.

“I want to see what their preliminary aggression is towards other males: whether they fight with each other, how often and under what circumstances,” says Corbin.

She will then apply a substance called methoprene, which mimics a hormone known to influence bee behaviour, to the carpenter bees’ abdomens.

“We’re going to observe their behaviour after a day or so to see if the elevated hormone level increases the male carpenter bees’ aggression and territoriality towards other males in any way,” Corbin says says.

The ability of male carpenter bees to guard nests could also have an impact on young bees’ survival and female reproduction.

Previous research has shown male carpenter bees are getting smaller on average. Lower hormone levels could result in less guarding of nests by the males, with a possible impact of more predators attacking bee nests, Corbin says.

Insecticides contain methoprene and other materials, known as juvenile hormone mimics, that prevent insect larvae from developing to the adult stage.

“Since bees are key pollinators for a variety of plants and crops, further research on the effects of juvenile hormone mimics on bees’ behaviour will enhance our understanding of whether these human-induced changes to the environment pose a risk to wild bee populations,” says Corbin.

Corbin is a member of Brock University’s Bee Lab, a grouping of undergraduate and graduate student researchers conducting projects under the direction of Professor of Biological Sciences Miriam Richards.

The lab studies the behaviour, evolution and ecology of bees, mostly in Niagara, with an emphasis on sweat bees and carpenter bees. Much of the research occurs in human-modified landscapes, such as former landfill sites.

Corbin’s research is being funded by a graduate student scholarship from the Natural Sciences and Engineering Research Council of Canada.