The Museum's Sensational Butterflies exhibition is definitely the fluttery flavour of the week. Not only has an incredibly rare half-female-half-male butterfly hatched in the exhibition's butterfly house very recently, Sir David Attenborough also made a very special appearance there today.

The rare dual-sex butterfly recently hatched in our Sensational Butterflies exhibition is a great mormon, Papilio memnon, from Asia. One half is female, with paler colours and blue, red and tortoiseshell flecks. The other half is male and is darker.

The discovery of this unusual dual-sex butterfly - such creatures are called gynandromorphs - caused huge excitement in the Sensational Butterflies exhibition when it was originally spotted. Gynandromorphy happens very occasionally across a range of species, from spiders to crabs. The word comes from gyn which is Greek for female and andro which is Greek for male.

Luke Brown (below right), manager of the exhibition's butterfly house says:

'Pure bilateral gynandromorphs are incredibly rare. I have only ever come across two in my whole career. So you can understand why I was bouncing off of the walls when I learned that a stunning half male, half female bilateral gynandromorph had emerged in the puparium at this year’s Sensational Butterflies exhibition. Many permanent butterfly exhibitions will go through their entire existence without ever seeing one of these rarities.’

The gynandromorph butterfly, however, may not be around for much longer. These species, sadly, only live for two to three weeks.

Read the news story and learn more about the gynandromorph discovery at Sensational Butterflies

Our other exciting and famous visitor to Sensational Butterflies today, which some lucky schoolchildren were lucky to catch a glimpse of, was Sir David Attenborough. He was here to help launch the Big Butterfly Count project organised by the Butterfly Conservation group which asks us to help record butterfly sightings from 16 to 31 July.

Children from The Russell School in Richmond with Sir David Attenborough are charmed by a swallowtail at the Big Butterfly Count launch in our butterfly house this morning.

'Butterflies are one of the stars of the British countryside. Summer just wouldn’t be summer without them' says Sir David

It's the second year running for the Big Butterfly Count and last year more than 10,000 people took part with 189,000 butterflies counted This year's results may help reveal the impact of our record-breaking spring weather.

Our Sensational Butterflies exhibition with its butterfly house full of 100s of live exotic butterflies and moths is highly recommended for a summer holiday visit. Open until 11 September 2011. Tickets £3.50.

As you approach the butterfly house marvel at the glorous outdoor garden (above) where you can learn butterfly-attracting tips for your own garden. Inside the butterfly house, who knows what else may hatch in the coming months? You might even catch sight of the extraordinary Madagascar moon moth (right). But remember when you visit, it's hot, hot, hot in the house, 'cos that's the way the butterfly beauties like it.

Find out about our Sensational Butterflies exhibition

See some exhibition highlights

Buy Sensational Butterflies tickets online

The nationwide OPAL Bugs Count also asks you to look for butterflies, in particular the small tortoiseshell butterfly. There are a humungous 380,041 bugs counted so far at the time of writing, but it grows larger every minute!

Learn more about the butterfly life cycle

More photos taken at the Sensational Butteflies exhibition this week. Select images to enlarge them

It's always a pleasure to announce the opening of the butterfly house outside on the East lawn. And I am so glad the sun shone today when the Sensational Butterflies exhbitiion was unveiled officially to the public. I know the butterflies inside the butterfly house love it so when it does.

Sensational Butterflies opened today, 12 April, on the Museum's front lawn

New features in this year's exhibition like the butterfly puddle (below), cocoon handling and a crawl-through chrysalis, are just some of the things to delight children and adults alike.

Left: The hatchery in the butterfly house, where butterfly life begins. Right: Butterfly puddle, where male butterflies sip

But really it's about the butterflies themselves. Watching the different tropical species flutter around so gracefully in all their glorious colours, shapes and sizes, while you marvel at how they sense the world. Trying to identify species as you spot them - there are handy identification charts around to refer to.

Remember to get your butterfly stamper card stamped as you go through each of the five sensory zones. You can pick one up at the ticket desk entrance. Outside in the garden, things are beginning to grow and you can find gardener's tips for attracting butterflies.

There are over 10 different species of swallowtail butterfly (left) in the house this year and as in previous years, blue morphos (right) are in great abundance.

Have a look at the exhibition highlights slideshow to see some of the reasons why you should visit our butterfly exhibition this year.

Enjoy the Sensational Butterflies highlights in the slideshow

Sensational Butterflies is open all through the summer and I'll be updating you with news along the way.

When you leave the butterfly house, check out the butterfly gift shop. If you go with children, of course they won't let you leave until at least one pair of deely boppers is on someone's head.

Tickets for the exhibition are £3.50 each and children aged three and under get in free.

You can book tickets online or buy them at the butterfly house ticket booth.

Another nice thing about today's exhibition opening is the news that a new butterfly species from Peru, the zebra-like ringlet butterfly, has been uncovered in the Museum's collections by Blanca Huertas, our butterfly curator. Splendeuptychia mercedes differs from its closest relatives by having broad stripes on its wings, resembling that of a zebra’s.

'Despite it not being the first time that I have identified a new butterfly species, it is still exciting,’ says Blanca. ‘Almost half of the world’s butterfly species are found in South America, and it is amazing we are still finding new ones there.’

Read the news story to find out about the new zebra-like ringlet butterfly discovery

It seems like only a week ago that the front lawn outside the Museum was a mudbath. But now as I write, thanks to sunny dry spells, we have the roof on the butterfly house frame. And work is firmly underway for its metamorphosis into a fully-foliaged and delightfully decorated home for the first live butterflies arriving at the end of the month.

Our Sensational Butterflies exhibition opens to the public on 12 April and tickets are on sale now.

Julia butterfly, Dryas iulia, one of the unusual species coming to Sensational Butterflies. These bright orange beauties have been spotted drinking tears from caiman eyes in Brazil. They are among a few butterflies in the world to do this.

I asked Rob, who's supervising the building work, how it's going: 'The main challenge is the weather – we basically have to turn a muddy field into an exhibition that will take 1000s of people walking over its floor surface, without it turning back into a muddy field again! It’s always a challenge, and every year we tinker with our ideas. The whole exhibition takes 4 to 5 weeks to build. Being a  tropical environment inside the house means that its humid, and the flowers and plants in there need loads of watering every day, which is really the worst thing you can do to a floor which was recently wet mud.'

Rob also told me that the butterfly house is actually an agricultural building, the same farmers use to grow crops of tomatoes or flowers. But the material it’s made from is a type of plastic that’s very flame-resistant, this is why it looks different from a normal agricultural building, which would just be covered in polythene.

The race is on: Turning a muddy field into a beautiful butterfly house and garden must be done in 4 to 5 weeks

It's the fourth year running for the Museum's ever-popular outdoor summer exhibition and this time it's all about the sensory world of butterflies. We'll get to find out what it's like actually being a butterfly and experience things from their perspective as we explore five different sensory zones in the butterfly house.

There will be lots of fun things to do indoors - we have no outside play park this year - like touching a real cocoon, crawling through a chrysalis, and even sniffing your way around tropical plants. New additions to the house include the intriguing-sounding butterfly puddle display and the chrysalis crawl-through tunnel.

The outdoor garden will have a lot to live up to on last year - it was the envy of the everyone here at the Museum by mid-summer - and will again bustle with window boxes, garden plants and tips for attracting butterflies.

So to the beauties of the show. On 30 March, about 600 live sensational butterflies will be released in their new home for the exhibition's opening, along with 1200 pupae. Exciting species to watch out for in the house will be the noisy wing-snapping Cracker butterfly (below right), the Julia butterfly (above) which has been seen drinking tears from caiman eyes in South America, and massive Atlas moths (below left).

Species to look out for at Sensational Butterflies

Left: Is it a fern? Is it a spider? Nope, it's the Atlas moth, the largest moth species in the world.  Image Neil Gale, Magic of Butterflies House

Right: What's the noisiest butterfly in the world? Probably the Cracker butterfly, Hamadryas feronia. You might hear some snapping their wings at potential predators on your visit.

Select the images to enlarge.

What are you most squeamish about? Giant cockroaches, spiders, centipedes, scorpions, beetles or even moths?

Me, I'd say most of them, especially if they were the size of a hand or more. Luckily, most of the biggest bugs on our planet are usually found in jungle rainforests, savannahs and caves, or in the safety of our Museum collections.

However, this summer, some of our largest and heaviest insect and arachnid specimens are being let out to star in the Big Bugs exhibition at our Natural History Museum at Tring which opened yesterday and runs until 21 November.

The Australian rhinoceros cockroach is the heaviest cockroach in the world. A female was recorded at just over 1 oz (33.45gms).

From the safety of their exhibition display cases, despite my squeamishness, like many others I will find these mega mini-beasts utterly mesmerising to behold, and highly recommend a visit to Big Bugs. The exhibition is free.

Live creatures like the venomous Emperor scorpion and world's longest stick insect at 14 inches, are on show alongside many rare and incredible specimens from the Natural History Museum's collection. It's the first time that all these enormous bug specimens have been displayed together.

And it's not just the scary bugs and spiders you'll meet, but eye-catching beauties like the delicate Helicopter damselfly and Queen Alexandra's Birdwing butterfly, the largest butterfly in the world.

There will also be creepy-crawly activities for kids at the exhibition and other bug-related activities at Tring throughout the summer season.

The docile giant leaf bush-cricket from New Guinea has a maximun wingspan of 11 inches

The inspiration behind the exhibition is a recently published Museum book, Big Bugs Life-size by our Museum entomologist and bug expert, George Beccaloni, which features actual life-size pictures of each marvellous mini-beast included.

My favourites in the book are the nocturnal rhinoceros cockroach, which is the world's heaviest cockroach, and the giant leaf bush cricket with a wing span of a whopping 11 inches. But the white witch moth, below right, tops that with 12 inches and the greatest wingspan of any living insect.

Read the news story about the Big Bugs exhibition and book

The Natural History Museum at Tring is located in Hertfordshire.

Explore insects and spiders on our website. You can identify and discuss bugs on our bug forum