Migrant Butterflies in Eastern North America

     Like a large variety of birds moving north in spring to nesting territories and south in autumn to avoid northern winters, about seventeen species of butterflies engage in some sort of migration in North America.  And at least five common, fairly obvious kinds of butterflies, including red admirals, common buckeyes, painted ladies, question marks and monarchs, do so in eastern North America, including passing through and residing in Pennsylvania.  All these species, as adults, feed on flower nectar, except the question marks that consume rotting fruit, dung and carrion.  Field guides or the internet will give readers views of adult and larval forms of these interesting and remarkable butterfly species to see their beauties and aid in identification.  And those same sources of information will offer more facts about each species.
     Red admirals are beautiful butterflies that engage in massive movements north in spring.  A couple of years, for a few days early in May each time, here in Lancaster County, Pennsylvania, I have seen thousands of single red admirals everywhere fluttering low to the ground and steadily pushing north, creating remarkable sights.  Eventually females of the species rest on stinging nettle plants here and throughout the northeastern United States to lay eggs.  The resulting larvae consume nettle leaves and pupate by early June, coming out a few weeks later as another generation of red admiral butterflies, but in the north.  Some individuals of a later generation wing south for the winter. 
     Buckeyes are striking butterflies with two dark "eye" spots on each of four wings for a total of eight spots.  Those large spots startle and intimidate would-be predators that might want to eat buckeye butterflies.
     During each autumn, large numbers of buckeyes migrate south to peninsular Florida where they spend the winter.  The next spring, survivors push north again to recolonize the north, just as migrating birds do.              
     A lovely kind of butterfly called painted ladies live all over the world.  This species also annually migrates north and south, including populations that build up in Mexico and, eventually, pour north into the western United States in spring.  Adult painted ladies feed mostly on thistle nectar.
     Question mark butterfly caterpillars mostly eat the leaves of hackberry trees, nettles and Japanese hops, which is a kind of vine on partly shaded floodplains.  After pupating and emerging as adult butterflies, many of them migrate south to avoid the northern winter.
     But monarch butterflies are, by far, the most famous butterfly migrant in North America.  Each March, many thousands of surviving monarchs start north on migration.  Somewhere in the western United States, however, those butterflies that overwintered in Mexico stop, mate, lay eggs on milkweeds, the caterpillars' only food plants, and die.  The second generation of that year, which should have many more individuals than the first, also pushes farther north and east and does the same.  And that third generation continues the expansion of range and reproduction.  But the offspring of the third generation, which is the fourth generation for that year, does not mate.  That last generation of the year migrates south, starting early in September, and settles by early November into the same forested slopes in Mexico that their great-grandparents came from the spring before.  That fourth group had never been to those woods, but they go, unerringly, to them.  What a mystery!!  How do they know where to go?  Nobody knows.  But it is a miracle of nature, as is everything in nature on Earth, and in the universe. 
     We humans can't even begin to comprehend how wonderful this universe is.  There must be a higher power far greater than ourselves!  Meanwhile, all we can do is enjoy and appreciate nature, and thank that higher power for its presence.