How do insects survive winter?

In winter a lot of our wildlife starts to disappear. Many mammals hibernate, some birds migrate, and the butterflies and dragonflies we saw all summer are gone. But where?

In the current issue of Nature's Home, entomologist Dr Ross Piper addresses this question. Most insects, he tells us, synchronise their activity with the warmer weather – their ability to move, feed and reproduce is governed by the ambient temperature. So come winter, they need to find a way to survive the freeze. The insects we’ve seen all summer are still around, they’re just less conspicuous – both in appearance and behaviour.

Some insects hibernate, these ladybirds have entered a state of torpor for the winter known as diapause. Photo: iStock

Do insects hibernate?

Yes, some. Insect hibernation is known as diapause. A few adults insects are able to survive winter in a dormant state. They enter a state of suspended animation, finding shelter in homes, holes in trees, in leaf litter, under logs and under rocks.

Like mammals, these insects enter a state of torpor. Their metabolism slows and their temperature drops while their heart rate slows. Some insects produce anti-freeze chemicals that enable them to become “super-cooled”. These chemicals work to prevent build up of ice, which can rupture and destroy the insects delicate cells and tissues. In very low temperatures however, these chemicals can fail and the insect is killed by ice.

Who hibernates where:

Bees – many species are different. Honey bees last out winter in the hive, huddling together and remaining semi-active, while bumblebees hibernate. For many species of wasp and bee, only the queen hibernates. In the summer the queen mates and new queens are born. These new queens leave the hive and spend the winter buried in soil, while the rest of the colony perishes. Solitary bees, meanwhile, often seal themselves in hollow stems, or in bug hotels, to survive the winter.

Some bees hibernate beneath the ground. This ashy mining bee is emerging from a burrow. Photo: Ben Andrew (rspb-images.com)

Wasps – similarly to bees, all species are different. Some queens will hibernate while the others die off, and some solitary species will hide themselves away in plant stems and underground.

Ladybirds – You can find groups of ladybird beetles huddled together for warmth under tree bark or on plants.

Aquatic insects – many of the inhabitants of the common garden pond simply sink to the bottom, waiting out the winter insulated by the water above. The nymphs of a few species of dragonfly, however, will be active beneath surface.

Butterflies – You may find butterflies hibernating, hanging upside down inside your garden shed. Peacock butterflies hibernate, as do brimstones and red admirals.

For other species, their life cycle allows them to avoid the worst of winter. Many adult insects will die after breeding in the summer. The next generation then lives on and lasts out the winter as eggs or larvae. They are concealed in the leaf litter, soil or under bark, just waiting for the warmth of spring. 

You may find butterflies hibernating in sheds and outhouses. Photo: iStock

Do insects remain active in winter?

Yes, a great many do remain active. Rummage around in the leaf litter, delve into some grassy tussocks or dip a few ponds and you’ll find plenty of small animals. In some of these microhabitats the insulation provided by the overlying vegetation or water takes the teeth from winter’s bite, and the temperatures may remain high enough for activity to continue. 

A few species of spider remain active throughout the winter, and there are even a few unusual insects that are busy with courtship and mating during the winter, such as winter moths (Operophtera brumata) and winter gnats (Trichocera annulata).

Male winter moths are commonly seen in the glare of car headlights when driving near woods and hedgerows from late autumn through to February. The peculiar female with tiny, useless wings is more difficult to find, but look on various broad-leaved trees and shrubs such as oak, birch, hawthorn and heather. The eggs they lay on these plants hatch in early spring. Winter gnats can often be seen lekking in the depths of winter and are able to take to the air in temperatures just above freezing thanks, again, to anti-freeze chemicals.

Some butterflies, such as this painted lady, will fly south for the winter. Photo: Grahame Madge (rspb-images.com)

Do insects migrate?

Yes, a few do. Monarch butterflies are most famous migrant, travelling from the US to Mexico every year, and a few do turn up in the UK. Painted lady butterflies arrive in the UK every year from Africa, while clouded yellows can come across the channel is great clouds.

It's easy to make a winter home for solitary bees in your garden. Build one yourself or buy one from our shop. Photo Andy Hay (rspb-images.com)

Read more about how insects survive winter in your Winter 2018 issue of Nature's Home magazine, or learn how to help the insects in your garden.

Have you seen insects preparing for winter in your garden? Let us know in the comments below.