The Very Hungry Caterpillar, the classic children's picture book written and illustrated by world-renowned children's author Eric Carle, celebrates its 45th anniversary this month.

It remains one of the most widely-read children's books in the UK, selling over 36 million copies worldwide since its publication in 1969 and has been translated into more than 55 languages. It is known that The Very Hungry Caterpillar has sold the equivalent of a copy per minute since its release, with researchers estimating that the perennial classic is read an average of nine times a year by the nation's 5.5 million primary schoolchildren.

Eric Carle was born in Syracuse, New York in 1929, but in the mid 1930s his homesick immigrant parents moved back to Germany, and Carle only returned to the US as an adult. His father served in the German army and was taken prisoner of war by the Russians, and as a teenage boy Carle was conscripted to help dig trenches on the Siegfried line, a terrible time he has never forgotten. He trained in Germany as a graphic designer and began his career working in newspapers, with the New York Times, and later in the advertising industry, before turning to books full-time. Other of his best-known titles include The Very Busy Spider and A House For Hermit Crab. He spoke by email to Rosemary Goring.

RG: Is the very hungry caterpillar you in any respect?

EC: Yes, the character is me but it is also everyone because it is a book about growing up and being out in the world.

RG: Can you tell me a bit about your childhood in America and Germany, and about your parents?

EC: I started first grade twice, once in the US and once in Germany, both at the tender age of six. Two cultures, two languages, two different teaching methods. There have been many "door openers" in my life, including one of the most influential and important person, my first grade teacher in Syracuse, Miss Frickey. Miss Frickey encouraged my creative interests at that early age and impressed upon my parents that they must nurture and encourage my talents as a visual person, which they did.

RG: You are the third writer I've spoken to in the past month whose father was a prisoner of war. Do you think that influenced the direction your art and writing took?

EC: For me, I always wanted to make pictures. And certainly I have seen the use of colour in my books as a kind of antidote to the grays and browns of my childhood. I didn't really start writing until much later. But pictures and drawing was always something I wanted to do.

RG: You have said that the works of Brueghel and Klee have been an important influence; I wondered what writers, for children or adults, have shaped your work or your ideas?

EC: Yes, among some of my favourite artists are Paul Klee (1879-1940), with his colourful, dreamlike paintings; and Pieter Brueghel (1525-1569), who painted peasants and landscapes of central Europe that remind me of where I grew up in Germany. Other illustrators whose work I admire include Leo Lionni, Maurice Sendak, Jose Aruego, Lisbeth Zwerger, Mitsumasa Anno, Ezra Jack Keats, Jerry Pinkney and Chris Van Allsburg. Each of these picture-book artists has an individual and distinctive style and approach, and each one speaks from his or her soul. And another influence is certainly my father. When I was a young child, we would go walking, observing the insects and creatures we came upon.

RG: What makes a great children's book?

EC: I think for me a successful picture book must be well-designed. With my own work, my aim is to simplify and refine, be logical and harmonious.

RG: What is it about the natural world and its creatures that so inspires you?

EC: My father used to take me out into the woods when I was a child. He pointed out animals to me or would peel back the bark of a tree and show me the creatures who crawled about. I have a special place in my heart for the small and often unnoticed creatures.

RG: Do you ever see your own influence on the work of younger illustrators?

EC: The greatest compliment to me is when I receive letters and art work from children who are working in a similar style of collage. Occasionally I see some illustrators who have mimicked my tissue paper collage style in books. So be it.

RG: Did returning to America as a young man change your art or your outlook in any significant way?

EC: I feel so fortunate to be able to do the work that I love and to have had so many people in my life who have supported my work, who have been "door openers" for me. One of these was Leo Lionni who was very kind to me when I first came to the US as a young man in 1952 and helped me to get a job at the New York Times.

RG: The time you were working in New York for an advertising agency seems to have been the same era as portrayed in the TV series Mad Men. Have you seen it, and do you recognise the culture and the kind of characters it portrays?

EC: Yes, I am familiar with Mad Men and I was working for an advertising agency in New York in the early 1960s. Eventually, it was too many meetings for me. I wanted to do the design work and the picture-making. When I started working on books for children - in particular working with author Bill Martin Jr on his book Brown Bear, Brown Bear - I was set on fire and felt I had found my true course in life.

RG: Did your own children love your books when they were young?

EC: My children were older than the age of my readers when I started to create books for children. But they were the inspiration for some of my books including Papa, Please Get The Moon For Me, which is dedicated to my daughter who asked me to do just that.

RG: Has the world of illustrated books changed much in 45 years?

EC: The biggest change in my lifetime has been the advent of the computer in the world of publishing. It has changed everything from the editing of the text to the laying out of the book and now some illustrators are using computer programs to actually create the illustrations right on the computer screen; something I will have a hard time doing. But, for a book to work, the basic ingredients remain the same: good ideas, good design and quality materials.

RG: Where do you live, and do you still manage to spend some time observing wildlife as you used to do?

EC: I spend half the year in the Florida Keys and the other half in the hills of North Carolina. In Florida, I enjoy watching the pelicans and iguanas and other wildlife near our home.

RG: Apart from the new edition of The Very Hungry Caterpillar, do you have any plans to celebrate this anniversary?

EC: I am a bit of a hermit, just like the Hermit Crab in my book, so I will most likely spend the day at home with Bobbie [my wife]. But it is wonderful to hear about the celebrations and programmes happening around the world. I am very gratified by this.

The Very Hungry Caterpillar is published by Puffin Books, priced £6.99