Long-distance mystery of the butterfly navigators

Recent days have seen small arrivals of immigrant red admirals and painted ladies as well as more substantial numbers of humming-bird hawk-moths, with as many as 30 counted at Spurn.

They are all likely to have started their journeys in North Africa or southern Europe. How can apparently fragile insects find their ways over such large distances?

That question sprang to mind as I relaxed on the deck of a cruise ship docked on the outskirts of Archangel, in northern Russia.

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I was looking south-eastward across the wide expanse of the River Severnaya Dvina to the forested bank beyond.

Suddenly, a moth dropped down on the deck close by, soon to be followed by a stream of butterflies and other moths.

There were several moorland clouded yellows, a large white, a female cranberry blue, and they all were heading roughly north-west.

However, I missed the star sighting of a swallowtail made by my wife while I had rushed across the deck to try to photograph another moth which had paused briefly.

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Fortunately, a fellow passenger, Dr Gillian Mawby, had photographed one on her tour of Archangel and kindly provided the picture used here.

I was surprised to discover that swallowtails were found so far north and, in fact, extend way beyond the Arctic Circle.

We have a very sedentary population in Norfolk, but the continental version – same species, but different race – is far more widespread and mobile. It is also less colourful.

The intriguing fact regarding the swallowtail, and, indeed, many other continental species, is that the further east you go, the more northerly the range extends.

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In spite of the long dark winters, the summer season of 24-hour sunshine can provide a butterfly’s ideal warmth.

But back to the question. Why were all the butterflies and moths apparently moving in line across the ship?

While there could be many reasons, there is growing evidence to suggest that some butterflies and moths, like some birds, can ‘see’ and follow magnetic lines of force.

There is little doubt that migratory species invariably fly north-westward towards the magnetic north pole and quite often they move in long lines as though locked into an invisible flyway.

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Our cruise also took us to several Norwegian ports and at Tromsø, well to the north of the Arctic Circle, we were surprised at the amount of snow still lying on the mountains on June 27.

Crew members who travel this way every year had never seen so much in June before.

That, in turn, could have a bearing on our own winter to come.

However, in spite of a coolish edge to the wind, a visit to Tromsø’s botanic garden revealed a reassuring list of butterflies.

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There were small and green-veined whites, common blues, small coppers and – a real rarity for anyone from England – a scotch argus.

They may look fragile, but butterflies are amazingly adaptable creatures.

Butterfly Conservation’s Big Butterfly Count runs from today to July 31.

This is a chance for everyone to join in and help assess the state of our butterflies, and it involves only 15 minutes of your time.

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For details and a chance to download a useful ID chart, do take a look at www.bigbutterflycount.org

Howard Frost is a volunteer for Butterfly Conservation Yorkshire, a branch of the national organisation.

Contact via: www.yorkshirebutterflies.org.uk where you can also find the latest reports.

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