I’d seen a couple of these plates before—BibliOdyssey has a post about Séguy’s insect art—but not the book as a whole. In addition to the butterfly portraits there are also a number of suggestions for textile designs based on butterfly wings. Papillons was published in 1925. Five years later Séguy produced a collection of Art Deco designs, Prismes, which was highlighted a while ago, and which is now also available at the Internet Archive. The Prismes plates tend to abstraction but nonetheless feature some stylised natural elements, butterflies included.