Calgarians may have noticed an increase in ladybugs in their gardens this fall.
But insect and gardening experts say the insect could be an invasive species, as ladybugs prepare for winter this year.
According to Biology Insights, as daylight hours shorten and temperatures drop in the fall, ladybugs seek suitable overwintering sites, like household gardens.
This seasonal behaviour in ladybug species causes increased sightings among Calgarians, specifically in community gardens.
Sheryl Normandeau, a well-known community gardener in Calgary, has written thirteen gardening books.
Normandeau said ladybugs will go out and scout areas around the city where they can build up fat storages for the winter. The beetles will then go into diapause, a sleep-like state that insects enter to save energy.
“If they find any good food sources, they will release a pheromone that will attract other ladybugs to that location, they’ll get together anywhere they can,” said Normandeau.
Since ladybugs are cold-blooded, they take in warmth from their environment.
They aggregate together on warm surfaces like tree trunks or under leaf piles to conduct heat. According to Incredi Grow Garden Centre, the increasing summer aphid population has boosted the fall ladybug population.
Local gardener Jennifer Hoglin sees ladybugs regularly during the fall. When she cleans up in preparation for winter, she always leaves behind leaf piles for the ladybugs.
“Our beneficial insects, like ladybugs, spend overwinter in the leaf piles. It helps regulate the beetle’s heat, allowing them to have an easier time surviving the winter,” said Hoglin.
Not the beetle Calgarians think
While Hoglin is seeing more ladybugs in her garden, she is also noticing the increasing appearances of the invasive Asian Ladybeetle.
The Asian Ladybeetle was brought into North America in the 1970s to help control pests in agriculture. Now they threaten native species of ladybugs.
The physical difference between an Asian Ladybeetle and the ladybugs native to Calgary is most obvious when looking at the pronotum, a body part behind the head.
On native species, the pronotum is black with two white spots on either side. However, the Asian Ladybeetles’ pronotum will be shaped like a black ‘M’. Asian Ladybeetles are also slightly bigger in size and come in a variety of colours, including red, orange, yellow and sometimes beige.
“They are not a problem because they eat pests in our garden, they are a problem because they take away from the native population,” said Hoglin.
Jackie Lebenzon is a zoology and animal physiology professor at the University of Calgary. Lebenzon also does research on environmental insect physiology.
If the Asian Ladybeetle population continues to grow, they might outcompete the native ladybugs, she said.
Lebenzon states that the native species of ladybugs may begin to slowly diminish due to the increasing amount of the invasive Asian Ladybeetle.
“That’s always the case with invasive species,” Lebenzon said. “They are a threat to native ones.”