Hampshire and IOW Wildlife Trust – Jan 2022

Logo for Hants and IOW Wildlife Trust

Where do butterflies go in winter?

Think of butterflies and usually we associate them with sultry summer days, but have you ever wondered how these delicate insects survive harsh winters in the UK?

Butterflies are ectothermic – or cold-blooded – meaning they cannot regulate their own body temperature and instead rely on external heat sources to warm up. This is why butterflies perch on leaves to bask in the sun or, conversely, seek shaded spots to cool down.
Butterflies struggle when sources of heat become harder to find, hence why British winters pose a problem. To overcome temperate climates, butterflies have adapted in remarkable ways to survive.

The most common way butterflies overwinter in Britain is either as a caterpillar or chrysalis. To protect their soft and vulnerable bodies, caterpillars find refuge at the bottom of plants or bury themselves in leaf litter or soil where they wait, hopefully undisturbed, until spring. This tactic is used by 42 of Britain’s 59 butterfly species, including orange-tips and common blue.

Another option, and one of the safest, is to wait it out as an egg. The brown hairstreak is one butterfly that employs this strategy.

Comma Butterfly © Amy Lewis

Comma Butterfly © Amy Lewis

Less common is the method chosen by five of the UK’s most recognisable butterflies, namely brimstone, comma, peacock, small tortoiseshell and red admiral. These species overwinter in their adult forms and, in late summer or early autumn, will seek out safe and relatively warm spaces, such as inside sheds, garages, log piles or even rabbit holes. They wake when temperatures rise and so are occasionally seen on warmer days in the depths of December and January.

Finally, the humble painted lady butterfly escapes the cold of British winter by making an epic migration to northern Africa in an incredible quest for warmer climes.

Despite these mighty displays of adaption, butterfly numbers in Britain are decreasing rapidly. Formerly common species, like the small tortoiseshell, have fallen by 80% in Southeast England since 1990.

But there are several ways you can help these amazing insects:

  • Delay cutting back old plants and tidying up leaf litter until spring to provide butterflies with places to overwinter
  •  Leave a wilder area of your garden, with long grasses, ivy, shrubs, weeds and nettles to provides vital butterfly habitat
  • Plan to plant some nectar-rich plants in your garden or window box for butterflies when they wake up in spring. Pollinator-friendly options include cowslips, rosemary, forget-me-knots, bugle, sweet William or heather
  •  If you find a butterfly in your home, garage or shed, carefully catch the butterfly and place it in a cool spot. Once the butterfly settles you can gently move it to an unheated room in a shed, porch or garage. Remember to let the butterfly out of the building when it awakens in spring