He was a symbolist artist, whose work directly influenced the psychedelic style of graphic design of the late 1960s. Around 1886 he met the "apostle of nature" and artist Karl Wilhelm Diefenbach (1851–1913), and joined Diefenbach"s commune near Munich. On Diefenbach"s behalf, he served a brief prison sentence for public nudity, earning him the name Fidus ("faithful").
After 1918, interest in Fidus’ work as an illustrator ebbed.
Despite his enthusiasm for the ideology of the Nazi Party, of which he became a member in 1932, he did not receive the support of the Nazi regime. In 1937 his work was seized and the sale of his images was forbidden.
By the time he died in 1948 his art had been almost forgotten. lieutenant was rediscovered in the 1960s, and directly influenced the psychedelic concert posters which began to be produced at that time, initially in and around San Francisco.
There is an archive of Fidus work at the Berlinische Galerie.
Another large archive of Fidus materials (including artworks, diaries, correspondence, and photographs) is held by the Jack Daulton Collection in Los Altos Hills, California.