Is Winter a Buzz Kill?

Spring is a time of year where it feels like mother nature’s heart starts beating again.  We’ve already seen the first snowdrops, crocuses and daffodils, but what else can be seen at this time of year? Well, on a sunny day you may notice the first pollinators of the year, as Brimstone butterflies (Gonepteryx rhamni) and queen bees emerge, but where have these insects been?  When we think of hibernation, we may think of bats huddled together in their roosts or bears having their winter slumber in dens, but can something as small as an insect survive the winter? Read on as Meg Stone, Graduate Ecology & Environment Consultant at STRI, tells more.

Brimstone butterfly overwintering under a holly leaf (National Trust).

Strictly speaking, insects don’t hibernate, and while some species such as the Painted Lady butterfly (Vanessa cardui) or the Silver Y moth (Autographa gamma) migrate to warmer locations, those that remain in countries with temperate climates throughout winter, like the UK, have in fact evolved to withstand the cooler temperatures.  Brimstone butterflies are one of four resident butterfly species that overwinter as adults in the UK, their closed wings perfectly mimicking the underside of a leaf.

Comma butterflies use trees to overwinter on, as once they close their wings, they look just like a dead leaf which minimises the chance of them being predated.  Both the Peacock (Aglais io) and Small Tortoiseshell (Aglais urticae) butterflies also adopt the ‘the dead leaf look’ when at rest with wings closed and will remain in this posture whilst they overwinter in buildings, hollow trees, or woodpiles. You can see from the images below how well these butterflies would be able to camouflage against a tree trunk or inside a dark building.

Some butterflies may have sought out the warmth of a house at the end of summer and settled there to overwinter.  As the weather gets warmer, so do our houses and these butterflies may be tricked into thinking it is time to emerge.  Putting these butterflies outside will not help them as it is still too cold and many of the plants they rely on for nectar are not flowering yet, such as dandelion, thistle and knapweed.  If you find a butterfly in your house, the Butterfly Conservation Trust recommends catching the butterfly and putting it in a box in a cool place for 30 minutes to make it calm and then try to gently encourage the butterfly onto the wall of an outdoor building that is not heated, such as a garage, shed or porch. Make sure there is an open window or some sort of exit in the building that the butterfly can fly out of when it is ready to emerge in spring.  If you don’t have a suitable building to release the butterfly in, try to keep it as cool as possible and then release it in a period of warm, sunny weather.  Like many animals, including humans, Peacock butterflies do not like to be disturbed when they are asleep.  They will make this quite obvious by flashing their wings and making a hissing sound by rubbing their hindwings and forewings together! 

Certain moth species overwinter too, such as The Herald (Scoliopteryx libatrix) which hibernates in caves, sometimes in great numbers.  It has even been found to hibernate right next to bats, which if not hibernating themselves would be more than happy to help themselves to this free buffet! Some lepidoptera species overwinter as pupae in leaf litter which is what this Pale Tussock moth caterpillar will have been about to do when I found him in December 2019 (below right).  You can read more about lepidoptera species and how they cope during winter on the Butterfly Conservation and Woodland Trust websites.

Another group of key pollinators that are emerging now are some bee species, but why are the first ones we see so big?  Well, these are the queen bees that have been in a dormant state throughout winter and have now awoken as the weather gets warmer.  According to the Bumblebee Conservation Trust some queen bees can hibernate for nine months, that’s nearly three quarters of their life!  Bees are not able to mimic dead leaves or camouflage, so they burrow into well-drained soil where they are hidden from predators and protected from diseases.  They are known to dig small tunnels, roughly 10 cm long before excavating a small hole where they stay throughout the winter. You may think that the soil insulates them, but actually they often choose north-facing banks, which aren’t exposed to low winter sun and some queen bees have been found to survive temperatures of minus 19!  If they were exposed to warmth of the sun they would be tricked into thinking it was spring, but would quickly find there would be no food available and most likely die of starvation.

Like bees, it is only the queen wasps that ‘hibernate’, whilst the rest of the colony die, including the old queen.  Instead of burrowing into the ground, they opt for the warmth and shelter of lofts in houses or barns.  Ladybirds also hide away from the cold weather that winter brings with some gathering in large numbers. 7-Spot Ladybirds overwinter in natural crevices such as under bark, as do 2-Spot Ladybirds and Harlequin Ladybirds which may also find shelter around window frames, so open your windows with caution!

So now you know where some of our key pollinators go over winter, in fact many of them don’t go anywhere, they are just experts in camouflage or find brilliant hiding spaces.  It won’t be long now until we see many more insects in our gardens and local green spaces, so keep a look out!

Don’t forget that there’s plenty you can do either on the golf course, in your garden, or even on your window sill, to ensure that you can sustain bees and beyond. Have a read of our past pollinator articles for tips, head over to Syngenta Operation Pollinator for inspiration, and delve into the new guidance for golf courses and how best to manage them for bumblebees to see how you can improve your facility for biodiversity.

Meg Stone