Hibernating insects in your home

In winter it is logical that we see fewer insects in our gardens. Being cold-blooded, insects need the warmth of the sun to stir them into action but you can guarantee that on a warm day, even in the middle of winter, there will be insects around and sometimes plenty of them. 

Do moths, butterflies and other insects hibernate?

Insects seem so fragile with delicate wings and such small bodies it is incredible to think that they can survive the cold of a British winter, but many do. Although this is not technically hibernation (which is a process warm-blooded creatures do) the outcome is the same, and the word is often used to describe overwintering insects.

The more accurate term is diapause, a state of dormancy that butterflies, moths and other insects go into to pause development over the winter months.

To cope with freezing conditions many insects change their biochemistry during autumn. In particular they create more glycerol which lowers the freezing point of their blood; in short they produce their own anti-freeze.

Even so, they still need to find somewhere sheltered from the coldest winter weather and this is the reason for us finding occasional butterflies in out-houses, and even spare bedrooms at this time of year. And while some species might wake up and flutter around in the depths of winter, others will be dormant as caterpillars of pupa wrapped in leaves, tucked into tree bark or even buried underground.

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Overwintering butterflies

Most British butterflies hibernate as eggs, larvae (caterpillars) or pupa (chrysalis) forms, but we have at least four species of butterfly (including brimstone, small tortoiseshell, comma and peacock) which can overwinter in their adult form in Britain. Some migratory species, such as red admiral and clouded-yellow butterflies, will try and hibernate but are unlikely to survive a cold, damp British winter.

During winter butterflies often wake, aroused by the warmth of the sun, or our central heating, and fly around for a few hours before settling down to sleep again. It is obviously better for them if they can remain in hibernation until such time as there are flowers from which to find food.

Find out what you can plant to attract butterflies into your garden

Overwintering ladybirds

The ladybird is another insect which hibernates in Britain. They tend to tuck themselves away in amongst ivy, or maybe in cracks around our windowsills, but many find themselves in the bark of evergreen trees. As a result we might accidentally bring them into our houses on Christmas trees.

If you find one hibernating ladybird there is a good chance of there being more because when these delightful insects locate a suitable hibernating space they excrete a pheromone to attract others, and you can end up with a 'loveliness of ladybirds' overwintering in your house or garden. In late autumn (October and November) you might see groups of them flying around your house and climbing on walls, looking for somewhere safe to hibernate.

Gardeners have good reason for trying to attract and look after their ladybirds. For one thing they eat aphids and greenflies; it is much better to have ladybirds on hand than to use chemicals to tackle this problem.  

Overwintering moths

One of the most likely British moth species to be found in the home over winter is the herald moth. This species has a flight season which begins in autumn and concludes in spring. Between the two periods it hibernates in cellars, caves, sheds and sometimes houses. Some moths, most notably the December moth, might still be on the wing in early winter.

Like butterflies, moths mainly hibernate as eggs, larvae or pupa, and rarely in their adult form.

What to do when hibernating insects wake up

If you have insects which are trying to hibernate in your house but which keep waking when the central heating comes on, the best thing to do is to catch them and move them to an environment with a more constant temperature, such as a shed or garage. 

When you find hibernating ladybirds on your living Christmas tree the ideal solution is to move the whole tree outside to a sheltered location.

What can you do to provide for overwintering insects?

If you want to provide a safe space for insects to hibernate the best thing you can do is provide the right plants and have plenty of untidy and overgrown areas. Ivy is perfect, not only does the evergreen foliage provide plenty of sheltered nooks and crannies for insects to hide in but the flowers provide a vital source of nectar and is one of the preferred food plants of the holly blue butterfly, which overwinters in their chrysalis on the ground near the plant. Old wood, such as tree trunks and piles of logs and sticks, can also provide a safe spot to overwinter.

Leaving the long, dried out stems in a herbaceous border up over winter is also good for wildlife. Not just for the insects themselves but also for the garden birds who will need to eat the insects to survive.

Hibernation boxes are sold but because of the risk of them heating up in warm weather you are better off providing a more natural hiding places.

Find out more about looking after your garden wildlife, including the importance of biodiversity and the best plants for a wildlife-friendly garden

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