Every year, Southern England becomes the stage for a remarkable sight when 3.5 trillion flying insects, equaling the weight of 20,000 reindeer, migrate across the country! Among these insects are the Painted Lady butterflies, the subject of a recent discovery among scientists and butterfly enthusiasts.
The Painted Lady butterfly (Vanessa cardui) has a 4-7.3cm wingspan and often populates dry open areas. Every spring they journey from their overwintering grounds in North Africa and the Mediterranean region to the UK, Asia and Northern Europe. These butterflies obtain average altitudes of 500m, can reach 30mph in favourable conditions, and can do a 9000-mile round trip from Africa to the Arctic Circle! For many years it was a mystery where Painted Lady butterflies went in the autumn, whether they died in the UK or made a return journey, as they fly at such a high altitude and could not be seen by butterfly observers. It was recently discovered that the Painted Lady butterflies do make a return journey in autumn, returning to favourable temperatures further South.
These butterflies are unique due to their migration being the longest-ever recorded flight for butterflies. These migrations can take generations, as they lay their eggs in the UK, and the offspring continue the migration South to southern Europe and North Africa, although not all participate, and some may not survive the harsh UK winters. As they undertake continuous, year-round mating, painted ladies can stop, breed and die at locations along the migration route.
How do they know when to start the migration? The caterpillars of Painted Ladies grow while the days are lengthening, to then fly northwards, and when the days shorten the butterflies know to travel south to warmer climates.
Painted Ladies are the only butterfly found in Iceland and since the 1970’s there population has increased by 32%! In the UK they feed on, amongst other plants, Teasels, Ivy, Ragwort, Heather and Hawkweed.
Although the migration of Painted Lady butterflies are one of a kind, other migratory insects are worth keeping an eye out for.
Sometimes we experience mass migrations of insects in summer and autumn. Between 10 and 25 billion medium and large insects move back and forth out of regions in Britain. This includes hoverflies for example, where 4 billion come to and from Britain each year, and they are essential for pollination and natural pest control.
Mass migrations truly can be a shocking sight, for example in World War 2, military observers reported a ‘golden ball’ drifting over the channel and thought it was poison gas, only for it to be migrating Clouded Yellow butterflies.
We also host other insects on their migratory journeys, such as the Red Admiral. This butterfly is extremely common in spring and throughout summer too, usually spotted near flowers such as Buddlea. They make their journeys from North Africa and continental Europe, arriving in the UK in Spring. They lay their eggs in the UK, meaning new butterflies are around from July onwards.
We also host Hummingbird Hawkmoths in Spring, who usually live in Central Asia and in the Mediterranean region. They’re named for their similarity to hummingbirds, feeding on nectar using their long beaks. Hummingbird Hawkmoths have very good memories, and often return to the same flowerbeds every day at the same time. They breed in the UK, and due to their inability to survive the winter they make return migrations in Autumn.
If you are lucky enough, you might be able to spot a Monarch Butterfly which makes occasional, sporadic appearances in the UK. It is believed that strong winds may carry individual Monarch butterflies across the Atlantic ocean into the UK. They’re native to the US and can fly up to 100 miles per day.
Migratory insects that visit the UK undertake incredible journeys driven by instinct and environmental cues, playing an important role in pollination, pest control, and ecosystem balance. Remember the next time you’re looking at a Painted Lady butterfly for example, it has taken 9000 miles and many generations to get there!
What to do in September
Obviously keep up the watering in sustained hot weather. For years now we have been having sunny and dry Septembers
Top up the mulch to retain moisture and keep weeds down (don’t forget they kept on growing until Xmas last year!)
Keep pinching out your tomatoes and sowing new rills of lettuce, radishes and spinach
Time to prune the bigger shrubs that have finished flowering like Wygelia, Philadelpus, and Sprirea- cut out the old flowering wood back to new growth that next year’s flowers will bloom from.
A harder cut of the Wysteria can wait till January so just lightly trim at the moment.
Mow your lawn on a higher setting now to keep moisture in the grass to help mitigate against summer browning in dry spells
Start planning where you want your bulbs to come out in Spring. You can order them online now for planting until November.
Where to go in September
This is your very last chance to see Chiltern Lodge this year. An exquisite garden developed by Lady Collum for over 40 years, it features a series of interlocking room, each one with a different purpose and feel- a herb garden, pool room, water rill room and classical sandstone summer house.
The garden is lovingly tended with an eye for detail and simple colour palettes.
It is open to the public just a few days of the year so put the date in your diary now.
Also put Sheffield Park in your diaries for October for its dazzling autumnal displays of mature trees.