These notes are intended as a summary of the early investigations into the habits of Glossina morsitans carried out in connection with the Luangwa Sleeping Sickness Commission. The part of the valley that has been examined is that lying between 12° S. and 13° 50' S., but it has been practicable to make only one journey to the eastern side of the river. This journey was undertaken in September and consisted of an examination of the Rukususi and Rukusi Rivers from the Luangwa almost to the Nyasaland boundaries. Hence these remarks apply mainly to the district immediately surrounding Nawalia, the headquarters of the Commission. The observations have been made during the period from August 1911 to the beginning of March 1912.