This has been another good butterfly year in Eliza Howell Park in Detroit, but now, in the middle of September, butterfly season is winding down. In a few weeks I won’t be seeing any here until spring next year.
Different butterflies have developed different methods of coping with cold winters they are not able to survive as active insects.The park species pass the winter (“overwinter” is the verb often used) in five different ways.
1.Some species migrate.
Most people are familiar with Monarch butterflies and are aware that they are long-distance migrants. The Monarchs that summer in this area overwinter as adults in Mexico.
Migration is not very common among butterfly species; only a few of the regular park species head south for the winter.
Red Admiral is an additional one that does.
The butterfly life cycle, described as “complete metamorphosis,” has four distinct stages: egg, larva (caterpillar), pupa (chrysalis), and adult. Some species overwinter in each of these stages.
2.Some species overwinter as hibernating adults.
Mourning Cloaks spend the winter in loose bark or logs or some similar location. They are among the very first butterflies of the year, appearing on warm spring days, often in late March.
Another early flyer each spring is Eastern Comma, also a hibernator.
3.Some species overwinter in the chrysalis stage.
This group includes a larger number than either migrants or hibernators. When the last generation of the year dies in the fall, there are no more adults until the following spring. In these species, this new generation will have spent a very long time inside before emerging from the chrysalis.
Both Black Swallowtail and Eastern Tiger Swallowtail overwinter in the chrysalis stage.
A common butterfly of gardens and parks in this geographic area, Cabbage White, is another example of a butterfly using this winter survival strategy.
4.Some species overwinter as caterpillars.
Probably more of Eliza Howell butterflies fit into this group than any of the others. Caterpillars “pause” their development for months (caterpillar hibernation?) before resuming their eating and growth in the spring.
Examples include some of my favorite species:
And Great Spangled Frittilary
5.Some species overwinter in the egg stage.
This does not seem to be a widespread practice. The pause in development here takes place even before the egg hatches. My example is Banded Hairstreak, not a butterfly that visitors to the park see frequently.
My collection of photos from this summer reflects my attraction to the butterflies of Eliza Howell Park. Knowing something about their diverse methods of living through the freezes of winter makes them even more fascinating when the weather warms again.