Monarch's Generational flight From Mexico to New England

It takes four or five generations of monarchs to reach New England, the Great Lakes, or southern Canada from Mexico. After mating in Mexico most females lay their eggs in Texas, then die. The next generation will continue north, mating and laying their eggs, living four to six weeks and then dying, until the fourth or fifth generation arrives in the northern United States and southern Canada.

As summer turns to fall, the sexual cycle of the butterfly stops, and the butterflies that we see in New England, the Great Lakes, and southern Canada begin the more-than-2,000-mile journey to Mexico, where they will spend the winter, live for about six months, and start the process all over again. Monarchs from west of the Rockies migrate to California; those from east of the Rockies head to Mexico.

These monarchs have never been here before. Much speculation exists about how they navigate their way. Magnetic fields in the earth, seasonal changes in the angle of the light and accompanying temperature shifts, the scent of last year's dying monarchs are all common theories, but there is no definitive answer.