When I was a child one of my favourite ways of passing the time was by playing with insects in the back garden. I was never short of creepy crawlies and was always intrigued by the number of different sorts I could find, writes Zahra Borno.

With the benefit of hindsight it's easy enough to see why there was no shortage in our garden - it is estimated that there are 18 quintillion insects on earth at any one time.

Leading insect expert Dr George McGavin, based at Oxford University's Museum of Natural History, has just published a new guide to the world's insects, called the Handbook of Insects.

Dr McGavin, assistant curator of the Hope Entomological Collections at the museum and a lecturer in biological and human sciences at Jesus College, has been gathering material used in the book for years.

And the guide has created a storm of interest already, as it includes one of the first pictures of a scarce and elusive 'ice bug' that inhabits the Rockies and parts of Russia. The northern rock crawler, scientifically known as Grylloblatta campodeiformis, is related to the cricket and cockroach, but is part of a seperate insect order, or family, discovered less than 100 years ago.

The pale brown and yellow insect, which only grows to a maximum of 1.2ins (30mm), has long atennae, no wings and when young, looks like an immature earwig.

It is so well adapted to surviving in colder parts of the northern hemisphere, that it could be one of several insect orders that would die of heatstroke if held in a human hand.

The ice bug is one of 600 species included in the new book. Others that have been highlighted include the recent insect immigrants which have come into Britain as 'stowaways - in the form of larvae in imported timber, for example, or by being blown across the Channel from Europe or northern Africa. These include several beetles and the French, or killer, wasp.

Dr McGavin says: "This book inevitably only scrapes the tip of the insect world iceberg.

"In Britain alone there are around 21,000 insect species and more than 1million species in the world.

"I have attempted to give an introduction to the incredible diversity of insects on earth. They are essential to the survival of people on earth because so many ecosystems work solely because of insects.

"Though they are individually small their importance is huge."

Dr McGavin has travelled as far afield as South America, Thailand and Africa for research purposes over the years, but has never actually seen a living ice bug.

He says: "It is a pretty rare animal. Originally it was thought to be a primitive grasshopper or cockroach. It was unclear where it fitted among the other insect orders so it was finally agreed that it was in an order all of its own.

"I expect most people in the UK won't ever see an ice bug. Even people in North America are unlikely to have seen them."

He says it is rare to find a new insect order, but finding a new species is far easier. Experts believe that only a fifth of the insects in the world have been identified.

Oxford's Museum of Natural History houses the second largest insect collection in the country with more than 4million specimens from all over the world on display.

But Dr McGavin agrees with me in that you need only look as far as your back garden to get an insight into the insect world.

He says: "There's more sex and violence happening in your back garden than you will ever see on screen, especially after dark. But because insects are so small they tend to get overlooked."

The Handbook of Insects, published by Dorling Kindersley, costs 9.99 a By Zahra Borno

zborno@nqo.com CREEPY COLLECTION: Dr George McGavin at the Museum of Natural History in Oxford (above) and examining an East African Assassin bug.

Picture: Kevin Harvey