Butterfly survival strategies for winter

07 December 2020 | Posted in Charlotte Owen , Insects
Butterfly survival strategies for winter
Chalk Hill Blue © Nigel Symington

By Charlotte Owen

WildCall Officer

Butterflies are creatures of the summer, of flower-filled days and long, sunny evenings. But, like all wildlife, they need to survive the winter too.

Most adults fade away by autumn, their bright colours muted and their delicate wings in tatters but their life’s mission complete. Hundreds of thousands of eggs have been laid and for nine butterfly species (including chalk hill blue, silver-spotted skipper and most hairstreaks) these will be the sole survivors. Their eggs are minuscule life support capsules designed to withstand the harshest of winter conditions and protect the developing larvae within, which spend up to eight months inside their armoured shells. They are dormant for much of this time, sleeping their way through winter, but by spring the tiny caterpillars will be ready to eat their way out and begin feasting on their food plants.

Most butterflies (31 species) overwinter as caterpillars, relying on camouflage and a good hiding place to keep themselves safe. They tend to hide in the leaves of their food plant or tucked away in grassy tussocks, trying their best not to be noticed. Some caterpillars (11 species including the whites, holly blue and speckled wood) pupate ahead of winter and survive as a chrysalis, wrapping their soft and vulnerable bodies in a tough protective casing and completing their metamorphosis next year. 

But a hardy few will overwinter as adults. Brimstone, peacock, comma, small tortoiseshell and some red admiral butterflies spend the late summer months feasting on nectar to build up as much body fat as possible. By now they will have found a cool, dry and sheltered spot to hibernate, perhaps in a garden shed, porch or garage, or in the natural shelter provided by dense ivy and stacked woodpiles. Sometimes they attempt to hibernate inside our homes, which can be problematic when the central heating kicks in and stimulates an early ‘spring’ awakening. If this happens, it’s best to carefully move them to an unheated outbuilding if you have one, or else keep the butterfly somewhere cool and release it outside on a sunny day so that it can find suitable shelter and head back to bed.  


  • Geraldine Pictor:

    14 Dec 2020 08:44:00

    This is so informative, as there were some things I wasn’t clear about regarding the butterfly’s life cycle. Caught sight of one only last week flying past our window. Could have been a tortoiseshell or possibly a red admiral.

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