Pollinator Migration: Who Stays?

By Ta’Leah Van Sistine, Marketing & Communications Intern

Some of our most memorable winter moments are made at the foot of a fireplace, underneath heaps of blankets or with sips from a warm cup of hot chocolate. This is how we avoid freezing cold temperatures winter brings. Interestingly enough, pollinators react similarly to this weather! As we discussed in the first blog of this series, some pollinators migrate to warmer climates where pollinator plants are still thriving. Other pollinators, though, remain where they are and hibernate during colder months.

In this second part of our Pollinator Migration series, we’ll explore some of the pollinators who, like some of us, bundle up and hide away to avoid winter’s wrath.

Butterflies

Different types of butterflies hibernate at different stages in their life cycle. For example, the Silver-washed Fritillary is one species that overwinters as an egg. The more common stage for butterflies to hibernate in, however, is the caterpillar. Viceroys, Tawny Emperors, Red-Spotted Purples, White Admirals and Hackberry Emperors all overwinter as caterpillars. Many of these caterpillars individually attach themselves to leaves or tree branches and wrap themselves in a tube-like shelter made of the leaf, while some like the Tawny Emperors gather in small groups and huddle in dried, curled up leaves to hibernate.

eastern tiger swallowtail butterfly

Easter Tiger Swallowtail

Others species, including  Cabbage Whites, Checkered Whites, Eastern Tiger Swallowtails, Black Swallowtails, Giant Swallowtails, Red Admirals and some Question Marks overwinter as chrysalises or pupas, and attach themselves to leaves and garden debris. Clouded Sulphurs, Orange Sulphurs and Variegated Fritillaries may choose the caterpillar or the pupa stage to overwinter. Lastly, Eastern Commas and Mourning Cloaks overwinter as adults. Hibernating adult butterflies can be found behind loose bark, in trees and in structures such as outdoor sheds or cellars.

Moths

It is more common for moths to overwinter as eggs, but some species like the Hawk Moths overwinter as pupae in warm cocoons underneath the ground. Other species such as the Herald Moth hibernate in cellars, caves, sheds and even houses at times.

crecopia moth caterpillar on leaves

Cecropia moth caterpillar

In the summer of 2017, we found a Cecropia Moth caterpillar in the Garden. It ended up hibernating that winter and emerged as a beautiful moth the next summer. Cecropias are the largest moths found in North America!

crecopia moth with cocoon

Cecropia Moth in the Garden.

If you realize one of these hibernating moths is in your own home and you notice it continues to wake up and flutter around, consider moving it to a location with a more constant temperature, like your garage.

Bees

Similar to butterflies, different species of bees hibernate in different ways. For bumblebees, all of the worker bees and the old queen bee die before winter commences, leaving the young queens as the only surviving members of the colony. These young queens then spend the fall season drinking large amounts of nectar, building up body fat and searching for a hiding place worthy of hibernation. If the bumblebees haven’t achieved a certain weight before winter, they will likely not survive, which is why it’s important for them to find many nectar-rich flowers in the fall. Bumblebees mostly overwinter underground or under tree roots and hedgerows.

bee on flower PC Chad Krause

Bumble bee PC: Chad Krause

Honeybees, on the other hand, overwinter as an entire colony inside of a beehive. When the temperature drops below 50° Fahrenheit, honeybees stop foraging and begin to surround the queen bee in the central part of the hive. The workers protect the queen from the cold temperatures by shivering, which raises the temperature to around 80°F and then 98.6°F when the queen begins to lay eggs again. Honeybees consume their stored honey throughout the winter so they can produce the necessary amount of body heat required to maintain a constant temperature in their cluster.

Just like pollinators, we humans all endure these Midwest winters differently. For those of us who look forward to venturing back indoors after encounters with cold air, ice and snow, we may not be too different from many of our neighborhood butterflies, moths and bees after all. Keep an eye out for our next part in this series “Pollinator Migration: Where Are They Now?” to learn where migrating pollinators end up in the winter!

Also remember to check out our first post in this series, “Pollinator Migration: Who Goes?”

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