Monarch butterflies: The Methuselah Generation flies instinctively back to Mexico via Texas
Gary Clark,Correspondent
Sep. 23, 2023
[ The only migrating butterfly:
A series of generations of monarch butterflies live 3-6 weeks each, then when its time for them to migrate the "Methuselah generation" migrates and flies south to southern Mexico where they live till February when it migrates back to central TX where they die and the short generation pattern returns.
How in the world did this "evolve by natural means?" ]
 1of3Monarch butterflies are migrating through the Texas Hill Country to coastal areas.
Kathy Adams Clark Show More
It seems improbable that fragile-looking monarch butterflies wafting through the skies across Texas could be on a 2,800-mile direct flight. They are leaving their northern breeding grounds for winter homes in a pine-oak forest preserve near Michoacan, Mexico.
What’s more improbable is that these butterflies, weighing less than a dollar bill and flying on black-laced sunset-orange wings spanning 4 inches,have never made the flight to Mexico before. They’re instinctively following the route of their ancestors going back untold centuries.
The southbound migratory monarchs are called theMethuselah Generation, the final generation of monarchs on northern breeding grounds.They’re the only monarchs that live long enough to fly to Mexico, spend the winter and begin the return trip in early spring. Preceding generations of monarchs during the past spring and summer lived a mere three to six weeks.
Migratory monarchs from eastern North America will travel along Texas coastal regions toward Mexico. But monarchs from the midwest and central Canada will travel along a diagonal path 300 miles wide from north-central Texas through the Hill Country and across the borderbetween Laredo and Del Rio.
Monarchs
- Monarchs arethe only butterflies that undertake an annual fall and spring migrationbetween breeding grounds and wintering grounds.
- While eastern monarchs migrate to Mexico for the winter, western monarchs west of the Rockies migrate to California’s Pacific Coast from Santa Cruz to San Diego for the winter.
- Monarchs breeding in north central states follow a wide path along the Interstate 35 corridor, which has been named the Monarch Highway, traversing six states, including Texas.
- Governments, companies and conservation organizations have implemented the management of beneficial habitat for monarchs along the I-35 corridor.
- During the winter of 2022-23, eastern monarchs declined by 22%, according to surveys by the World Wildlife Fund of Mexico.
- For more information, visit journeynorth.org.
Here’s what we know about the ability of migratory monarchs to accurately orient their southbound migration:
A pair of molecules inside their brains acts like a magnetic compass to orient them.
Diminishing autumn daylight activates the molecules, causing the butterflies to head south. Monarchs additionally orient themselves by the sun, but they’ll follow a precise ancestral route, even on cloudy days.
We don’t know what makes them head to ancestral wintering grounds. Scientists think an inherited genetic code directs them, but the specific genes in the presumed code remain unknown.
Most migratory monarchs will be on Mexico’s wintering grounds near Michoacán by late November.They’ll enter a state of diapause, or nonbreeding, until late February, when they’ll begin the return trip toward North American breeding grounds.
Butthey won’t live to complete the trip. They’ll instead breed and lay eggs on newly emerged milkweed, especially in Texas, because that’s about as far north as the wintering population can travel.
The trip back to northern breeding grounds involves an improbable leapfrog migration, assuccessive generations of monarchs breed, lay eggs and die, until a final migratory population emerges to make the trip to ancestral northern breeding grounds they’ve never seen.
Houston Chronicle
Breeding range
Del Rio - Laredo TX
Michoacan
Twelve Native Milkweeds for Monarchs • The National Wildlife Federation Blog (nwf.org) |
