Like many of our migrating birds, the monarchs gather in the fall for an epic journery. My friend, Mr Science (Gary) gives the following succinct explantion.
MONARCHS PRODUCE FOUR GENERATIONS EACH YEAR. THREE OF THESE GENERATIONS ONLY LIVE ABOUT ONE MONTH EACH, BUT ONE GENERATION(THE 4TH GENERATION) LIVES FOR ABOUT 8 MONTHS AND THAT IS THE GENERATION THAT EACH FALL MAKES A 1400+ MILE MIGRATION TO MEXICO. THIS FOURTH GENERATION WILL MIGRATE TO MEXICO, OVERWINTER THERE, LAY EGGS IN MEXICO AND THEN DIE. THOSE EGGS WILL HATCH MAKING A NEW 1ST GENERATION THE WILL MIGRATE AS FAR AS ABOUT N. TEXAS-LAY THIER EGGS AND DIE. THE NEXT TWO GENERATION WILL REPEAT THIS CYCLE AND HEAD FARTHER NORTH EACH TIME. THE 4TH GENERATION IS BORN UP NORTH AND IS THE ONLY GENERATION TO MIGRATE TO MEXICO IN THE FALL.
His notebook "Nature Notes" on the flora and fauna of Fillmore County, Minnesota can be found at