The Respiratory Exchange of the Desert Locust (Schistocerca Gregaria) before, During and After Flight
Authors: Krogh August , Weis-Fogh Torkel 
Published: April 2021

During the last two decades the knowledge of the physiology of heavy muscular work has increased considerably, and the high metabolic rate of flying insects has attracted particular attention. Jongbloed & Wiersma (1935), Chadwick & Gilmour (1940), and Davis & Fraenkel (1940) have reviewed the literature concerning the metabolic rate of flying insects. More recent investigations dealt mainly with the nature of the fuels combusted or with other aspects of insect flight. Most of the experiments referred to below dealt with measurements of the oxygen consumption of insects performing flight movements in a relatively small container. In this respect and because generally the animals were suspended and the natural locomotion was prevented the conditions of flight were abnormal. However, these limitations concerning the conditions of flight are probably of minor importance when we are interested mainly in the order of magnitude of the metabolic rate and in the nature of the fuels combusted, and with these limitations in mind, the present state of knowledge might be summarized: (1) During flight the oxygen consumption is considerably increased and has been estimated at about 100 1. O2/kg. body weight/hr. in bees (Jongbloed & Wiersma, 1935), flies (Davis & Fraenkel, 1940), and butterflies (Zeuthen, in Krogh, 1941). This means that the metabolic rate during flight in some insects increases 100 times or even more compared with the metabolism during rest. In an extensive and very interesting series of experiments Chadwick & Gilmour (1940) and Chadwick (1947) have demonstrated that various species of Drosophila consumed only 20 1. O2/kg./hr., a figure which was indirectly verified by Williams, Barness & Sawyer (1943) and Wigglesworth (1949). In the above-mentioned papers by Chadwick, and a paper by Chadwick & Williams (1949), the metabolic rate was correlated with the wing-beat frequency.(2) The respiratory quotient (R.Q.) during flight was measured in bees (Jongbloed & Wiersma, 1935, in Apis) and flies (Chadwick, 1947, in Drosophila). In both cases the R.Q. equalled unity, indicating the combustion of carbohydrates, and this interpretation seems to be correct, glucose and glycogen being utilized as fuels in Apis (Beutler, 1937) and Drosophila (Williams et al. 1943; Wigglesworth, 1949) respectively.(3) After the cessation of flight a small oxygen debt was demonstrated in Drosophila (Chadwick & Gilmour, 1940). The debt was abolished in less than 2 min.

August Krogh’s unpublished analyses of the R.Q. of flying Lepidoptera gave values about unity, and so it seems reasonable to assume that the higher insects derive the energy for flight movements from the combustion of carbohydrates. Many insects generally considered primitive from a morphological point of view are, nevertheless, excellent flyers in one or more respects. The dragonflies, for example, are second to none as far as the flying speed and the refined regulation of the flight movements are concerned, and locusts are able to endure sustained flight for several hours every day during a considerable period of time. As the migrations of locusts are of great economic importance, it is thus of interest from both practical and theoretical points of view to study the metabolism during flight in these relatively primitive insects. The purpose of the present paper has been to study some quantitative and qualitative aspects of the combustion of flying locusts.