"the very hungry caterpillar" uses distinctive collage illustrations (carle's third book, and a new style at the time), 'eaten' holes in the pages and simple text with educational themes – counting, the days of the week, foods, and a butterfly's life stages. there have been many related books and other products, including educational tools, created in connection to the book. the caterpillar's diet is fictional rather than scientifically accurate, but the book introduces concepts of lepidoptera life stages where transformations take place including the ultimate metamorphosis from 'hungry caterpillar' to 'handsome butterfly', and it has been endorsed by the royal entomological society.