Butterfly watchers say another wave of Red Admirals is headed for Toronto
By Melissa Wilson
April 23, 2012
The butterflies are here. Normally, this wouldn’t be leading news material, but last week they came early, and they came in droves, cascading through the skies and taking up residence in the city’s trees and parks. They’re everywhere.
The Red Admirals would usually be in the southern U.S. — particularly Texas and Iowa — this time of year, according to Antonia Guidotti, an entomologist at the Royal Ontario Museum, just starting to think about heading north. Like in Toronto, the weather in the south was warmer than usual, creating ideal conditions to reproduce, meaning that by mid-March there were a lot of adults ready to migrate. “They came riding in on that strong wind current we say on Sunday and Monday,” says Guidotti. “I’ve never seen anything like it.”
The Red Admirals’ early arrival, though, is less notable than the sheer size of the flock. Like something out of a Hitchcock film, the butterflies simply invaded.
According to Maxim Larrivée, a butterfly researcher at the University of Ottawa, southern Ontario in April might see a handful of these butterflies if the climate was right, but last week saw millions. “Within 48 hours, they moved from Point Pelee to New Brunswick to North Bay,” says Larrivée. “They covered a million square kilometres.”
“In Ottawa, there’s still snow on the ground,” he says, “but there’s a thousand butterflies in the maple trees on my street.” In Toronto, they’ve been spotted all across the city. Larrivée says he’s never seen this many butterflies come to Canada.
Glenn Richardson, president of the Toronto Entomologist’s Association, said the same, describing last week’s event as an “explosion of butterflies.”
That said, “an explosion of one species doesn’t mean an explosion in another,” says Richardson, though he says he’s noticed a general trend of increased butterfly populations in southern Ontario in the past few years. He suspects it’s related to global warming. “Over time, we’re going to see a change,” he says.
David Gibo, professor emeritus in the biology department at the University of Toronto’s Mississauga campus, is more to the point regarding the larger implications of the butterfly invasion. “I can tell you right now what it means,” he says. “It means nothing. It was a fluke.”
Red Admirals don’t live very long, and their primary goal in life is to reproduce, creating several generations of butterflies each season (that is, the Red Admirals that piloted into Toronto last week will not be the same ones to leave this coming fall, but rather their great-grandchildren). “They’re quite a successful species,” says Gibo, “And the amount that they are able to build up and reproduce depends entirely on the conditions around them.”
In short, Red Admirals reproduce massively, a female perhaps laying 100 eggs on average. She hedges her bets, because a whole host of things can affect her eggs before they reach maturity: The eggs can be eaten by parasitic wasps, caterpillars get washed away by rain, they get diseases or infections, they gets stepped on by a cow, or a parasite lays eggs inside of one of their bodies that then bursts out of its stomach like that scene in Alien.
It happens. Being a butterfly can be pretty dangerous.
All each female needs is for two of her 100 eggs to survive to maturity for the population to remain stagnant. If conditions are good, and four survive instead of two, the population doubles. If they’re very good, like we saw this year, and eight or 10 survive — ironically, according to Richardson, the storms and tornadoes that plagued the southern United States recently were beneficial to the butterflies, allowing more nettles to grow for them to eat and killing off many of the parasitic wasps, who are their main predators — then we get an explosion.
But that still means that 90 eggs were lost. “Nature is very wasteful,” says Gibo. On the large scale, “small changes in the survival can result in very big changes.”
Interestingly, while Toronto’s concrete towers and often-unreasonable climate might seem a poor home for butterflies, Richardson says the habitat is quite ideal.
Aside from the numerous green spaces tucked into corners of the city, Toronto sits on the cusp of both a Carolinian forest (think the hard-wood forests in High Park) and a transitional forest (think the sugar maple trees in North York), which means there’s double the diversity of species. Additionally, says Richardson, “if they’re migrating from the south and have to cross a large body of water, like Lake Ontario, the first land they see will be Toronto, so that’s where they’ll want to stop and settle for a while.”
Though the arrival of the butterflies has raised a lot of questions, Larrivée insists that even though it’s unusual, it’s nothing to be concerned about. “There’s nothing dangerous about this. Just go out and enjoy the beauty of the flowers, and take the opportunity to your children to connect with nature and butterflies,” he says. “Because they’re everywhere.”