So I was watching the latest episode of PBS's NOVA. This episode was
The Incredible Journey of the Butterflies, a tale about the Monarch,
which (in North America) over winters in the Mexican mountains, then
in life stages journeys to Canada where the big journey begins with
the last of the seasonal adults returning to Mexico.

At one point in the show an entomologist in Texas, was hunting down
the migratory butterfly flock in his VW Vanagon Westfalia.