Research in Copenhagen corresponds roughly with the period during which Weis-Hogh was Professor of Zoophysiology at Copenhagen, 1958-1966, although there is some material that overlaps with section B. The papers include background material to the discovery of resilin (C.1-C.6), and cover the work Weis-Fogh carried out on several aspects of insect physiology while in Copenhagen, including the tracheal system and muscle action potential in locusts (C.12-C.30). A grant from the United States Air Force European Office of Aerospace Research in 1965 helped to support further investigation of resilin through different types of microscopy, and the results of some of this research appear in C.37-C.103. The work was continued in Cambridge after Weis-Fogh's appointment to the Chair of Zoology in 1966 (see D.1-D.26).