 From 1938 to 1959 Haas was curator at the department of lower invertebrates at the Field Museum of Natural History in Chicago.Haas' specialty involved the study of land and freshwater snails, as well as research of the family Unionidae (freshwater mussels).He performed extensive field investigations in Norway (1910), Pyrenees, Spain, France (1914–19), southern Africa (1931–32; as part of the Hans Schomburgk expedition) and the Americas (Brazil, Bermuda, Cuba, Canada).