saw him regularly until van Emden was expelled from National Socialist Germany for having a Jewish mother and wife.

Hennig developed a deep friendship with Emden's successor, Klaus Günther. Hennig concluded his studies with a dissertation entitled, Beiträge zur Kenntnis des Kopulationsapparates der cyclorrhaphen Dipteren. By this time, Hennig had published eight scientific papers. Besides his 300-page revision of the Tylidae (now classed as Micropezidae), there were further papers on Diptera and