METABOLISM OF INSECTS 



545 



van't Hoff's formula, but between zo.9 

 and Z7.2.5°C. the increment in carbon 

 dioxide production was proportional to 

 the increase in temperature, and above 

 Z7 it decreased, as did the velocity of 

 development increment. 



Loeb and Northrop (16) found that 

 the duration of life of fruit fly (Drosophila) 

 cultures was a function of temperature, 

 the insects living longer at lower tem- 

 peratures. They also found that the life 

 of Drosophila was normal only at tem- 

 peratures above io° and below 30°C. At 

 5 or less the duration of life of the adult 

 was less than a week, while at 15 it was 

 9Z.4 days. At • temperatures above 27. 5 

 the coefficient for the rate of growth be- 

 came negative. Temperatures beyond the 

 normal range were incompatible with the 

 life of the organism. They also found 

 that the nature of the food influenced the 

 duration of life and that an adequate food 

 supply was necessary for work on the 

 influence of temperature. 



Allee and Stein (1) studied the carbon 

 dioxide output of May fly nymphs in 

 relation to light. Changes in metabolism 

 accompanied changes in light reactions. 

 Nymphs positive to light had higher 

 metabolic rates than the negative nymphs. 

 Negative nymphs when exposed to light 

 gave off more carbon dioxide. In condi- 

 tions of depressed metabolism, insects 

 were negatively phototropic and vice 

 versa. 



Bodine (3) made an excellent study of 

 the water content and the rate of me- 

 tabolism in grasshoppers. These insects 

 responded to temperature changes as did 

 other cold-blooded forms; that is, in- 

 creased temperature caused increased re- 

 spiratory rates. Carbon dioxide deter- 

 minations were made using single animals 

 and each determination extended over a 

 period of thirty minutes to one hour. 

 There was a difference in carbon dioxide 



output according to the species, the differ- 

 ence being correlated probably with its 

 mode of life. Active species had a higher 

 respiratory rate than more sluggish types. 

 The rate of carbon dioxide output was 

 higher for animals lighter in weight and 

 decreased progressively as the animals 

 increased in body weight. 



Bodine found that the amount of carbon 

 dioxide given off by the grasshoppers 

 decreased during successive periods of 

 starvation. During the early period this 

 decrease was rather slight and gradual, 

 but later marked drops were noted. This 

 decided decrease was due probably to the 

 fact that at this time all residual food in 

 the intestine had been utilized and body 

 reserves alone were being used. Bodine 

 found that after feeding starved indi- 

 viduals an increase in the rate of carbon 

 dioxide output was evident. 



Dirken (9), working on the cockroach, 

 observed that the oxygen consumption 

 was influenced by temperature, but not in 

 the sense stated by van't Hoff's Law. 

 As the temperature varied, "the gaseous 

 exchange was probably modified by in- 

 fluences from the nervous system. ' ' More 

 carbon dioxide was consumed in initial 

 exposures to high temperatures than in 

 exposures hours later to the same tempera- 

 ture. He suggested an adaptation in the 

 gaseous exchange by the body cells. 



Bodine (4) made carbon dioxide deter- 

 minations on both hibernating and grow- 

 ing grasshoppers at the same temperature. 

 The rates of carbon dioxide output for 

 hibernating animals at o-8°C. were noted, 

 being an eighth to a tenth of the rate at 

 room temperature, zo°C. The rates of 

 carbon dioxide output in hibernating 

 animals at room temperature remained 

 higher than in growing animals, suggest- 

 ing that the animals remained young 

 throughout the period of hibernation. 

 Bodine and Orr (5) studied the respiratory 



