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Flight of the Butterflies follows hundreds of millions of monarchs from Canada and the U.S. to their remote sanctuaries in Mexico.

The project to tag monarch butterflies and track their migrations between Canada and Mexico was launched more than 30 years ago by Fred Urquhart, one of Canada's leading entomologists.

The research initiative was inherited in the early 90s by Chip Taylor, a researcher at the University of Kansas, who has expanded the program, now known as Monarch Watch.

In close to 30 years, thousands of amateur biologists, retired gardeners and schoolchildren in Canada and the United States have volunteered their time to catch, tag and release more than a million butterflies.

The data collected from those insects has spawned a new 3-D IMAX film, Flight of the Butterflies, which premieres this month in Toronto.

The Globe and Mail interviewed Dr. Taylor on the film and on his work with monarch butterflies.

How do you catch a butterfly?

What I tell everybody is you have to think like a praying mantis. It means that you have to move slowly. You can't move fast. Because the thing about an insect eye is that the insect eye can pick up rapid movement and the insect eye is very poor at picking up slow movement. So that's what you're going to do to catch a butterfly: You're going to let it land on a flower, you're going to come up below it and behind it, and you're going to get about a foot-and-a-half away, and all of this time you're moving slowly and then – swoop! – it's in your net.

The net is the same? That technology hasn't changed?

No, that technology hasn't changed. You swoop it into the net.

But the tagging technology has changed quite a bit. Tell me about how the tags have improved.

I used Dr. Urquhart's tagging method for the very first year and I determined that I was never going to use it again. Too many inexperienced people broke the wings of the butterflies using his method. Too many tags were lost.

He'd developed a method of tagging them on the leading edge of the wing. Which I felt was going to damage the butterflies in some way, going to damage their flight.

We struggled to learn how to tag these butterflies. The new tag is based on a very good adhesive and we tag them on the middle portion of the hind wing. It's close to the centre of gravity for the butterfly so it doesn't interfere with flight.

What have we learned from the data you've collected from the butterflies?

One thing that came out of this that nobody realized is that the migration is very predictable. When I first got into this, the perception was that this was a phenomenon that was driven by the weather and only by the weather. It turns out that it isn't. The migration proceeds south about a month ahead of the first frost, proceeds on a very regular basis through the middle of the country and it coincides with the declining altitude angle of the sun. When the sun reaches somewhere between 56 and 57 degrees above the horizon at noon, the monarchs start their migration at every latitude. So in Winnipeg, for example, that's about the 10th to 12th of August.

How are monarch populations being threatened?

There's a big conflict in Canada between people that want to see this butterfly protected and people that are trying to eliminate milkweed. You can't do both, you have to protect milkweed to protect the butterfly. What's going on of course is our kind of insane desire to make everything look like our front lawn and to mow and use herbicides along all our roadsides – that has eliminated a lot of monarch habitat. The biggest impact has been development.

Monarchs need the milkweed to lay their eggs?

If you don't have the milkweed, you don't have the life cycle.

Have we seen an impact on the monarch population?

Oh yes. We've published two papers showing there's a statistically significant decline in the number of monarchs related to the development of use of herbicides on round-up ready corn and soybeans. Our population is now in the last ten years about 50 per cent of what they were in the previous ten years.

What was it like watching a film based on your life's work?

It's hard for me to watch this film without tearing up at certain points because it just sort of grabs you. The first scene, when you're suddenly in this absolutely magnificent forest that I've been in many times, it's just an experience.