It's been a great year for butterfly watchers. Fine, sunny weather during spring and early summer, especially in the south of Britain, has brought these winged wonders out in force. Admirals and peacocks, skippers and hairstreaks, blues and fritillaries, are all delighting us with their delicate shades and gaudy colours. My own garden in Somerset is currently awash with ringlets, green-veined whites and meadow browns, all classic butterflies of high summer.
So has it been a good year for butterflies? Given the previous paragraph this may seem like an odd question. But these creatures' life cycle is a complex one, and this glut of winged adults we have seen this year is not necessarily a reliable guide to the survival of eggs, caterpillars and pupae – the "savings bank" which will ensure these butterflies' long-term fortunes.
Now we have a chance to help the experts to find out how Britain's butterflies are faring, at a time of great environmental change. This week Sir David Attenborough launched this year's Big Butterfly Count, the biggest survey of butterfly populations anywhere in the world.
Run by Butterfly Conservation, Europe's largest insect charity – in partnership with Marks & Spencer – it aims to provide hard evidence for the rises and falls in the fortunes of some of our best-loved wild creatures.
And there is certainly cause for concern. As Sir David notes: "When I first moved to my home in Richmond upon Thames 50 years ago, my buddleia used to be covered with beautiful butterflies. Now I'm lucky if I see a Cabbage White."
Taking part in the survey couldn't be easier. During the next fortnight, we're asked to spend just 15 minutes counting how many of each different kind of butterfly we see. This can be in our gardens, on a walk in the town or countryside, or at one of many hotspots up and down the country. If you need help sorting out the trickier species, you can download a handy identification chart from the Butterfly Conservation website.
Last summer saw the very first Big Butterfly Count, during which more than 10,000 people logged more than 200,000 individual sightings. This still has a fair way to go to reach the half a million regular participants in the RSPB's Big Garden Birdwatch. But that survey started on a small scale too, yet in 30 years that has become the biggest citizen-science project anywhere in the world.
Richard Fox, the Big Butterfly Count's organiser, certainly has high hopes, and urges us to take part as a way of getting to know these charismatic and beautiful creatures. But he also points to the event's more serious side.
"Butterflies are in severe decline in the UK, indicating a worsening of the environment for much of our wildlife," he says. "Three-quarters of our 56 resident butterfly species have declined over recent decades and many are threatened with extinction. By counting butterflies for just 15 minutes, anyone can help Butterfly Conservation's scientists to get a better understanding of how butterflies are faring."
The survey is particularly crucial this year, coming as it does after very wet summers for our butterflies during 2007 and 2008, followed by slightly better years in 2009 and 2010.
Although this year started off spectacularly well, with its fine spring weather benefiting early flyers such as the orange-tip, the continuing drought has threatened the plants hosting the caterpillars of future broods. June, however, was cool and wet, which was bad news for this year's high summer butterflies.
Matthew Oates of the National Trust – who is known as "Britain's Mr Butterfly" – stresses both the scientific and spiritual importance of the Big Butterfly Count.
"Butterflies are a superb route into the wonderful world of nature," he says. "They guide us into the heart of the most magical landscapes at the optimum times of year, and are spirits of the living sunshine.
"The more you learn about them, the more there is to learn – which is why so many top scientists study them," he adds. "But they're unlikely to survive without our help. Their future is in our hands."
Oates's recent book, Butterflies, is both a handy pocket guide, and a paean to their sheer beauty, without whose presence our lives would be hugely diminished.
So whether you are an expert or a novice, surely it's worth giving up a quarter of an hour to help to save Britain's butterflies, and to reconnect with nature at the same time.
As Sir David Attenborough put it at the launch of this year's count: "If my heart is not going to be lifted by a butterfly because they have all gone, then my life will be very much the poorer."
Stephen Moss's new book – 'Wild Hares and Hummingbirds: The Natural History of an English Village' – will be published in September by Square Peg.
Your Big Butterfly Count guide
Butterflies can be fussy creatures, and need the right time of year, weather, habitat and food: nectar-bearing flowers for the adults, and food plants for their caterpillars. Even when you do see one, identifying it as it dashes by can be tricky. So here's a handy guide to getting to grips with Britain's butterflies...
1. Pick the right time of day
Most butterflies are on the wing during the warmest, sunniest time of day, from mid-morning to late afternoon.
2. Pick the right weather
Some butterflies do fly on cloudy days, but when the sun comes out they often emerge in really big numbers.
3. Start in your garden
Gardens can be surprisingly good for butterflies: they need nectar to maintain their energy levels, so flowering plants are ideal sources of food.
4. Explore farther afield
Check out your local park, the vegetation along river or canal banks, and even roadside verges, which can be havens for grassland species.
5. Think like a butterfly
Sunny, sheltered areas in your garden, the local park or in the open countryside are ideal places for butterflies to warm up, especially early in the morning.
6. Know your plants
The buddleia – also known as "the butterfly bush" – attracts a wide range of nectar-loving species including the peacock, comma and red admiral. Check out the caterpillars' food plants, too: find the right plant and you'll often find a butterfly laying its eggs there.
7. Approach carefully
Like most insects, butterflies are sensitive to rapid movement, as it warns them of an approaching predator. So approach them slowly and carefully.
8. Use binoculars
Binoculars aren't just for birding – they also give great views of butterflies, especially when they are basking in the sunshine.
9. Use a butterfly net
It's controversial but using a net to catch a butterfly enables you – and any children present – to take a really good close-up look. Be careful not to damage their wings when catching them, and always release them soon afterwards.
Counting is important, but the most crucial thing about this whole event is that it gives you the chance to discover the wonder of some of the most beautiful creatures on the planet: butterflies.
To take part on this year's Big Butterfly Count, visit: www.bigbutterflycount.org