The author describes these beautiful little volumes as “entomological pocket books.” His intention was that they be tucked into a pocket and carried on field trips. Their small size and purpose classifies these as field guides; their date of publication makes them very early field guides. Illustrated books of natural history at this time were much larger in order to more easily accommodate the lithographic stones or engraving plates used for illustrations.

Each illustration in this book show the complete life cycle of a butterfly: egg, larva, pupa, and adult, as well as habitat and the top and bottom surfaces of wings.