The Very Hungry Caterpillar, Eric Carle's holey, colorful children's book marks its 40th birthday (anniversary?) today. It was always a favorite with my children, who enjoyed the colors, the counting and the story itself. Anyone who has read it knows the joy of watching a child grasp for the illustrations, following the track of the caterpillar by worming little fingers through the holes in the fruits.

Carle's masterpiece has sold more than 29 million copies and been translated into 47 languages. It continues to sell about 650,000 copies a year.

Carle, 79, told USA Today that his original idea was A Week With Willi Worm, featuring a green bookworm that grew fatter and fatter. It ended with a lament: "Poor Willi." When his editor objected, they played around with other posssibilities, before Carle hit on the ending: a butterfly "It became a story about hope," Carle said. "This little, fat ugly thing ends up flying into the world as a beautiful butterfly."