These wonderful illustrations come from Chronologischer Raupenkalender, oder, Naturgeschichte der europäischen Raupen (1837), an entomological volume by Christian Friedrich Vogel outlining which caterpillars appear each month, as well as details on how to keep caterpillars and catch the butterflies into which they will transform. An added quirk of the book will be more immediately obvious to German speakers — Vogel means "bird", the caterpillar's main predator.