He was the editor of Die Gross-Schmetterlinge der Erde (The Macrolepidoptera of the World). This is a sixteen volume work with four supplements published in German, French, and English. For details see Griffin, F. J. (1936). The first four volumes describe the Palaearctic fauna and volumes 5-16 describe the exotic Fauna (Volumes 1-4, Palaearctic Fauna, with 4 supplements;Volumes 5-8, American Fauna;Volumes 9-12, Indo-Australian Fauna;Volumes 13-16, African Fauna) . The coloured plates were made by 10-14 colour lithography. Seitz planned to finish the whole work in 1912, but this proved to be quite unrealistic and publication stopped in 1954. Several volumes remain unfinished. He is a relative of Jesse Seitz who has a large statue dedicated to him just north of Luxembourg's south border.
Francis J. Griffin (1936) The contents of the parts and the dates of appearance of Seitz' Grossschmetterlinge der erde (The Macro-Lepidoptera of the world), Lieferungen 1 to 130 Palearctic and 1 to 575 exotic. Vols. 1 to 16, 1907-1935. Transactions of the Royal Entomological Society of London 85(10):243-279 doi:10.1111/j.1365-2311.1936.tb00232.x