MONARCH & MILKWEED
wE WERE IN Tamaulipas; it was late September. Strong winds were blowing ashore from the Gulf of Mexico, rising up the rain-soaked slope of the Sierra Madre, elevating the Monarch butterflies almost beyond visibility. Their light bodies had resolved into dark dots. Counting them was pointless. There were millions, more than millions. In flight, the dots moved up and down, but it was the mass that moved, as a unit, on the way to Michoacan.
Like many species of waterfowl, Monarch butterflies make passage along several flyways. There is not just one winter destination; west coast Monarchs do not usually go to Mexico. Routes to overwintering grounds in Mexico have been plotted. We know that Monarchs from midwestern and eastern states funnel through Texas, crossing the Rio Bravo. How they navigate is a mystery. The Monarch butterflies that overwinter in the conifer trees in Angangueo, Michoacan, and elsewhere in Mexico, are not the same butterflies that return to Connecticut or Ontario: an adult returning from Mexico may lay eggs in Texas, die, leaving the next lap of the journey north to its offspring.