This is an excellent field guide to identify butterflies. It has beautiful photographs and sorts them out into categories like swallowtails, checkered, folded-wing skippers, etc. It also has a small section with photos of a limited number of some eggs and caterpillars. Once you know what kind of butterfly you want info on, go to the page with more info on each species. There's also an index for plants, so if you find a caterpillar on a certain plant but don't know what species of caterpillar, you can look at the pages for species using that plant.