He spent 1933 to 1945 in Dusseldorf, returning to Sohl in 1945 to resume his teaching career, eventually becoming head teacher.
He later went on to become Professor of Biology at two teacher training colleges.
In 1921, Ermisch received a small collection of beetles, which he soon began to expand.
This work was to continue until his death, including collecting trips to the Caucasus and Bulgaria.
Unfortunately, during a move, some 73 of the 200 boxes containing his collection were destroyed, including all of the Mordellidae that he had described up to that time.