The reason why so many butterflies have been seen across Eastern Canada
Rain in an American desert, winds in Quebec and more time for reproduction than usual were all factors that lead to the massive increase in painted lady butterflies flitting through air over the last few weeks, according to Maxim Larrivée, the section head of entomological collections and research at the Montreal Insectarium.
“What happened this year is unprecedented.” Larrivée said. He explained this phenomenon is a combination of many factors. “Last winter, there were unusual rains in the Sonoran Desert where the butterflies spent the winter,” which led to a higher survival rate, he explained. In addition, strong southern winds in Quebec in April facilitated the butterflies’ migration north, which is why they showed up a month earlier than usual.
According to Larrivée, the swifter migration allowed the butterflies to produce in larger numbers. Normally, they have time to cycle through one or two generations each summer once they arrive, Larrivée explained. However, since they showed up so early this year, the butterflies had the chance to generate an extra life cycle. “This created this explosion of individuals,” Larrivée said.
There are also factors keeping the butterflies in Quebec longer than expected, Larrivée added. “Normally, when they migrate back to the south in the fall, they go up in the air column and they’ll migrate at 300 to 400 metres in the air,” he explained. “However, what happened this year is they faced heavier southern winds in early September, and that put them to the ground. They are now sitting and waiting for winds to shift from north to south so they can ride them and facilitate the migration.”
While there were some initial misconceptions among the general public about the type of butterfly filling the skies, Larrivée confirmed that most of the butterflies Quebecers have been seeing are in fact painted lady butterflies. “They are part of a group of butterflies from the gene called Vanessa [cardui],” he said, adding that “painted lady” is their common name. “A lot of people confuse them with monarchs because they are flagship migratory butterflies.”
The distinction, according to Larrivée, is that monarchs are bigger in size, with bright orange and black veins running through their wings. The wings of the painted lady, on the other hand, are brown in the centre, with orange patches visible when the wings are open. When the painted butterfly closes its wings, their mottled pattern blends with the ground. “The good thing about [the phenomenon this year] is that almost every Quebecer will now be able to distinguish a monarch from a painted lady,” Larrivée said.
According to Larrivée, the fall migration of these butterflies finally began in mid-September. “We have been stalled in this warm weather pattern with limited-to-no winds,” he explained. “Normally, the painted lady would take off within a few days after hitting contrary winds.”
However, Larrivée specified that this delay has nothing to do with the hurricanes pummeling the Caribbean in the last month. “I’m sure there are some larger global weather patterns that are influencing this, but I don’t think the hurricanes are related to their abundance,” he said. “We had a similar phenomenon in 2012, but it happened in early August instead of early September. It was a smaller magnitude, but it was historical from our standpoint and it lasted just a few days because the winds changed more rapidly.”
Outside of Quebec, there has also been an increase in painted lady butterflies around the Great Lakes of Ontario, Vermont, Maine and all the states bordering the Great Lakes. Once they begin migrating, the butterflies’ route takes them to the southern American states and northern Mexico. “There will be a few stragglers who will be a bit behind, but the bulk of them should be gone by Oct. 2 ” he said.
Larrivée is the founder and director of eButterfly, an international, data-driven project dedicated to butterfly biodiversity, conservation and education. According to Emma Despland, an associate biology professor at Concordia, eButterfly is a citizen science project where ordinary people can get involved in scientific research by taking pictures of butterflies they see around the world.
“We want to know where the butterflies are and when. So, either you hire an army of thousands of students across the continent or you ask ordinary people, ‘If you see one of these butterflies, let us know,’” Despland said. “It’s a way to get information and get people involved with science and the natural world.”
Two of the assignments in Despland’s class, Techniques in Ecology (BIOL 450), require students to use eButterfly as a resource. “In the first assignment, students have to go out and photograph three butterflies, identify them and upload their identifications on eButterfly,” she said, adding that this gives her students practical experience as naturalists. “I think that’s valuable for Concordia students because they’re very urban, so they don’t have much experience with the natural world,” she said.
Larrivée said he hopes to better map the migratory corridors of the painted lady butterfly to see if this species coordinates or aligns with the monarch. “I’d be really interested to use the sightings reported by our participants on eButterfly to determine what corridors they used to migrate and where to spend the winters in the south,” he said.
Students can contribute to the eButterfly project by sharing their observations and submitting photographs to eButterfly.org.
Graphic by Zeze Le Lin