To spot a butterfly: Insectarium asks for Montrealers' help counting monarchs

Montrealers are being called to action to help stave off the decline of one of North America's most celebrated residents.

The Montreal Insectarium launched its data-driven, Mission Monarch project this weekend, asking people to help locate monarch butterflies across the city.

The goal is to locate monarchs and milkweed — the plant on which the butterflies lay their eggs — to accurately map the butterflies' local habitat, explained the project's co-ordinator, André-Philippe Drapeau-Picard​.

"We'll be able to map the milkweed and monarch breeding precisely enough to locate the breeding habitat and protect some of them," Drapeau-Picard​ told CBC Montreal's Daybreak.

Hope to stave off the monarch's decline 

Drapeau-Picard said the monarch population has declined by about 80 per cent in the last 20 years, but "there's still a chance to save" the species.

One reason for its decline is that pesticides are killing the milkweed plant, which the monarch depends on for its survival.

This has led the Montreal boroughs of Saint-Laurent and Rosemont–La Petite-Patrie to start planting milkweed as part of the "Mayors' Monarch Pledge," a campaign in which mayors from 150 municipalities across North America are participating.

The hot weather this summer, however, has resulted in a monarch revival in Canada, which is seeing higher numbers of monarchs than witnessed in the past several years, he said.

In contrast, in Mexico, where the migratory monarchs spend the winter, the count shows that the butterfly is in a drastic decline.

The monarchs' 4,500-kilometre journey to Mexico each fall takes longer to complete than the butterflies' two-to-seven-week summer lifespan. 

That means that about four generations of monarchs will live and die before the great-great-grandchildren of those who first set out from Canada arrive in Mexico.

"There seems to be a mismatch between the summer population size and the winter population size," Drapeau-Picard said.

He said that's one of the major questions he hopes the data collected through Mission Monarch will help answer.

"Why is there that mismatch and what does it mean for monarch conservation?" he said.

Where should you look?

Where you find milkweed, you'll find monarchs, Drapeau-Picard said.

"Go outside, look for milkweed, the host plant of the monarch, [and] verify the presence of monarchs on those plants," he said.

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Drapeau-Picard said when examining the milkweed, people should look for eggs, caterpillars and adult butterflies flying around the plant.

He said the caterpillars are easy to identify because they're hairless, have two sets of horns on each side of their body, and are yellow, black and white.

"With those traits, you can be sure that you're looking at a monarch caterpillar," he said.

Mission Monarch also has a guide on its website to help people identify the butterfly throughout its lifecycle.

To report a monarch or milkweed plant sighting, or for more information about Mission Monarch, visit the project's website.