Abstract
At the end of the 1960ies I began my investigations on Ephemeroptera, researching the fauna of the Lake Constance area. For the beginner that I was, there were a lot of questions, uncertainties in determinations and suchlike. Who would be able to help me? There was only one person: Dr. Ingrid Müller-Liebenau, a leading German Ephemeropterologist. At that time she was going to finish the revision of the European species of the genus Baetis at the Limnological Station in Krefeld-Hülserberg. So in January 1968 I made a trip to visit her.