TRACHEAL RESPIRATION 129 



Respiration during flight. Flight requires an enormous ex- 

 penditure of energy which has to be provided by oxidation of 

 food. This was first shown by Marie Parhon (1909) who 

 measured the metabolism of a number of bees buzzing about 

 in a large bottle. The figure arrived at, 20 litres of oxygen 

 consumed per kg/h, was considered by many to be impossibly 

 high, but it has been verified and even exceeded in later 

 investigations. Kosmin et al. (1932) and finally Jongbloed 

 and Wiersma (1935) in flight experiments on single bees of 5-6 

 minutes' duration observed values of 90 1/kg/h, or for the single 

 bee, weighing 100 mg, 15 times its own volume per minute. 

 Kalmus (1929) succeeded in inducing long-continued sta- 

 tionary flight in a butterfly, Deilephila elpenor, weighing about 

 600 mg, and found C0 2 productions of only 6.3 1/kg/h, 1 but 

 Anne Raffy and P. Portier (1931) again obtained much higher 

 figures on different butterflies by nicotine poisoning which 

 simulates flight, and in quite recent unpublished experiments 

 Zeuthen in this laboratory found on Vanessa (atalanta and Io) 

 during actual flight values of 90 1/kg/h. The results represent 

 increases over the resting metabolism of the insects studied of 

 50 to 200 times. 



The enormous metabolic rate causes a considerable increase 

 in the temperature of a flying insect, and it is a very charac- 

 teristic fact, first observed by Dotterweich (1928), that many 

 insects cannot fly until their temperature has been raised to 

 a certain point, usually above 30°C. Dotterweich observed 

 that several species of butterflies would vibrate their wings 

 rapidly before flight and thereby raise the body temperature, 

 in these cases to 36°C, before flight could begin. 



It is a well-known fact that in the beetles belonging to the 

 Lamellicornia flight is preceded by a series of deep "pumping" 

 respirations, which were formerly thought to fill up the body 

 with air. Recent experimentation (Krogh and Zeuthen, 1 940) 

 has shown that in this preparatory period body temperature is 

 raised by static muscular contractions (demonstrated by 



1 The results appear 'doubtful, because the metabolism found during rest, 

 168 ml/kg/hour, is much too low. 



