Respiration and Tracheal Ventilation in Locusts and other Flying Insects

Abstract

ABSTRACT In small insects there is no need for respiratory movements because the rate of diffusion of oxygen and carbon dioxide is adequate even during flight, but when the thorax is more than a few millimetres in diameter the primary tracheae or the air sacs which supply the wing muscles must be ventilated (Weis-Fogh, 1964b). Apart from various auxiliary mechanisms described by Miller (1960 a, 1964), the respiratory movements are of two different types: the well-known abdominal movements which result in abdominal pumping of air and haemolymph and the little-known movements of the thoracic walls which are caused by the wing movements themselves and which result in thoracic pumping at wingstroke frequency (Weis-Fogh, 1956a, 1964a). The existence of a thoracic mechanism has been suspected for a long time (du Buisson, 1924; Krogh, 1941; Krogh & Zeuthen, 1941) but was denied by Fraenkel (1932a) who investigated the abdominal respiratory movements and their control in a variety of large insects during tethered flight. Lack of suitable methods seems to have prevented further studies.