In summer, you see butterflies everywhere but how do butterflies actually overwinter? Do butterflies hibernate? We clarify what butterflies do in winter.
Winter is a particularly stressful and adverse season for all garden animals. While many birds fly south for the winter, squirrels hibernate, and hedgehogs even sleep through the cold season butterflies seem to disappear without a trace in winter. Therefore, many wonder if and how butterflies hibernate. In fact, the numerous native butterfly species have developed quite different techniques to survive this season. What they are and how to help butterflies overwinter, you can learn from our article.
Do butterflies hibernate?
Animals that are warm to the touch, including reptiles and insects, often hibernate during the winter, also known as hibernation. But do butterflies also hibernate? This depends on the species: Many butterflies overwinter as caterpillars, chrysalises or eggs, as they are often much more robust at this stage. In these species butterflies die in winter if their short adult life span has not ended before then. However, it also happens that butterflies fall into winter torpor. In some butterfly species, adults also overwinter. Here the butterflies survive the winter by seeking out sheltered places and staying there until spring.
Tip – Caterpillars in winter: Many butterfly species do not overwinter as adults but rather in the caterpillar stage. How the caterpillars overwinter also depends on the species: Many caterpillars overwinter protected in the soil or under the bark of trees. Other caterpillars are almost defenceless against the weather in winter – the lesser purple emperor butterfly (Apatura ilia), for example, hangs on to its food plant throughout the winter. The caterpillars of the popular admiral butterfly (Limenitis populi) have developed a very special way to protect themselves from the weather: They spin themselves a winter lair, known as a hibernarium, in which they are protected as a caterpillar from wind and weather during the winter.
Where do butterflies overwinter?
Walking through the garden in winter, the sight of a butterfly is a more than rare occurrence. The question quickly arises: Where are the butterflies in winter? Basically, most butterflies look for a sheltered place in winter. Naturally, these are often tree cavities, spaces in stones or gaps in evergreen plants.
However butterflies are often found overwintering in the home. In particular, unheated rooms are predestined for butterflies overwintering indoors because the temperature does not fall below minus but at the same time low enough for winter torpor.
The only exception is the lemon butterfly (Gonepteryx rhamni): This butterfly is often found hibernating in what appear to be completely unprotected places. In fact, the small butterfly is not dependent on a frost-protected weather habitat, as it has built-in frost protection. By selectively releasing water, the lemon butterfly can lower its freezing point in winter – allowing it to survive temperatures as low as -20 °C without any problems.
By the way: The overwintering of butterflies does not only take place in Germany. Some species of butterflies, like birds, simply flutter south in autumn to tide them over during the colder months. For example, the wintering of the thistle butterfly does not take place in cold Germany but rather in warm southern Europe or even Africa.
Which butterflies survive the winter?
The number of butterflies that survive the winter as adult moths in our country is actually smaller than one might think: only seven of nearly 200 butterfly species survive the winter as butterflies. All other species overwinter as caterpillars, pupae, or eggs, or fly to warmer areas in winter. The lemon butterfly is most common in winter. Their ingenious antifreeze system means that no sheltered spot is needed for the citronella butterflies to overwinter – to the delight of many gardeners, who can spot the creatures in the snow-covered garden. Day peacock eyes (Aglais io) also overwinter in Germany – however, peacock eyes prefer to seek out a sheltered spot in winter. Also, the swallowtail (Papilio machaon) seeks a sheltered, frost-free place for overwintering. Large and Small Fox (Nymphalis polychloros and Aglais urticae), the Admiral (Vanessa atalanta), the mourning cloak (Nymphalis antiopa), and the C butterfly (Polygonia c-album) are also among the butterflies that overwinter as moths.
Which butterflies overwinter with us as adult moths?
- Common brimstone
- Peacock butterfly
- Large tortoiseshell
- Small tortoiseshell
- Mourning Cloak
How can I help butterflies in winter?
Garden animals in winter are almost always dependent on human help – butterflies are no exception. In particular, sheltered places for hibernation have unfortunately become rare. Those who want to help the butterflies overwinter should therefore first and foremost make sure to provide shelter: Dense climbing plants, piles of stones and brushwood, as well as dead wood and tree hollows are ideal for overwintering butterflies. Therefore, it is best to provide a varied garden with many wild corners, where there are enough hiding places for the little butterflies. Alternatively, an insect hotel or butterfly house in the garden can serve as weather protection for the moths. In addition, you can offer unheated garden sheds or tool sheds to butterflies for hibernation by leaving a window open a crack.
But butterfly-friendly plants are just as important to help butterflies overwinter as suitable shelter. After the end of hibernation, they not only provide the butterflies with much-needed nutrients, but they also serve as hibernation sites for many caterpillars during the winter. Therefore, plant out as diverse a butterfly-friendly seed mix as possible as early as spring or summer, and be sure to leave the plants standing in winter: After all, caterpillars can overwinter on them.
How can I help butterflies overwinter?
- Leave garden as close to nature as possible
- Set up butterfly house or insect hotel
- Leave the windows of the garden house and tool shed open a crack
- Sow butterfly friendly plants
- Avoid mowing butterfly-friendly plants in winter
It often happens to come across a butterfly in the winter. Especially when butterflies choose to overwinter indoors, animal and human often inevitably meet. The place where the butterfly wants to overwinter is decisive for what happens next.
If a butterfly has chosen an unheated room with temperatures below 12 °C, such as an attic or garage, it is perfectly safe to keep them indoors during the winter.
However, if the butterfly has chosen a room that is to be heated, it will need help to overwinter: The warm temperatures awaken the butterfly’s spirits and jolt it out of its winter torpor – in the worst case, the butterfly then dies after only a short time because it consumes too much energy.
To help the butterfly overwinter, carefully trap the animal in a cardboard box and release it in a more suitable location. When doing this, make sure that the animal has a way to escape from its winter quarters in the spring – an open window, for example, is a suitable escape route. If you find a butterfly outside during the winter, it is best to leave it in place so as not to disturb its winter torpor. In no case should you bring the butterfly into the warm house – this well-intentioned help, unfortunately, is often a death sentence for the colourful insects.
What do I do if I find a butterfly in winter?
- Outdoor location: If possible, leave the butterfly where it was found, never carry it indoors.
- Find site in unheated room (< 12 °C): Leave butterfly at site of discovery.
- Find location in heated room (> 12 °C): Carefully capture butterfly with a cardboard box and gently transport to a cooler location, at the new location ensure escape routes for spring.