Today in southeast Pennsylvania the high temperature was 22° Fahrenheit. Definitely not butterfly weather! However, as I worked on the WildsideNatureTours.com web site, specifically the Mexico Monarch Butterfly Tour photo gallery, I pondered the life-cycles of other butterflies, like the Eastern Tiger Swallowtails pictured here, too.
The Monarchs’ migration, and its trials, are well documented and followed by many each season. Monarchs are caught and tagged with tiny stickers so that researchers and citizen scientists can track their progress as they make their way to the mountains of Michoacan, Mexico. There they stay for 5 months, the only generation of Monarchs to live so long. The trees where they roost in a torpid state are at an altitude of about 10,000 feet. The trails can be rough for hiking and visiting the roosts by horseback is often preferred.
When they return north in spring, the long-lived generation lays its eggs… and dies. Each generation then proceeds progressively north to lay eggs and die, until the days get shorter and the waning light triggers the gene that causes the generation that migrates again to Mexico.
What about the Tiger Swallowtails? They pass the winter cold hidden out of the elements as pupae. In case you forgot, butterflies have multiple life stages in which they look very different. Egg, larval (caterpillar), pupal (chrysalis) and finally the beautiful adult winged creature we call butterflies. Other species of swallowtails found in my area, like Spicebush and Black Swallowtail overwinter as pupae as well.
We do have some northern species that hibernate as adults: Eastern Comma, Question Mark and Morning Cloak, to name a few. The Morning Cloak is often the first butterfly I see –fluttering in and out of the shadowed forest– as the days begin to stay consistently warm.
Other butterflies migrate, but none to the extent of the Monarchs. Their spectacle brings admirers from around the world to visit the mountains of Mexico. In only 12 locations, spanning a radius of 75 miles, all the Monarchs congregate by the hundreds of millions, covering the oyamel trees in a cloak of black and orange.