 Beginning in 1925, Ermolaeva created illustrations for children's books while working at DETGIZ, the Children's Division of the State Publishing House.She illustrated such books as “Top-top-top” (1925) by Nikolai Aseev, “Mnogo zverei” and “Rybaki” by Alexander Vvedensky, "Poezd" by Evgeny Schwartz (1929), “10 fokusov Chudodeeva“ (1929) by M. Il’in, "Ivan Ivanych Samovar” by Daniil Kharms (1930) and many others.From 1929 to 1931, she illustrated a series of 12 books based on Ivan Krylov’s fables.