Every autumn, monarch butterflies drift through my backyard in Austin, Texas. Their luminous orange-and-black wings spurred me to trace their migratory trail to the Monarch Butterfly Biosphere Reserve in the volcanic mountains of central Mexico.   With two girlfriends, I gazed in awe at millions of butterflies clustering in trees in their winter home in the monarch butterfly reserve.   Our small-group journey with Camiba Cultural Tours paired a monarch encounter with time in the colonial city of Morelia and visits to artisan towns in...