546 



THE QUARTERLY REVIEW OF BIOLOGY 



metabolism of the fruit fly, Drosofhila. 

 Ten pupae were used at one time, and 

 determinations of carbon dioxide output 

 were made on successive days. They 

 found that the weight decreased during 

 pupal development and that the oxygen 

 intake and carbon dioxide output de- 

 creased on the second day of pupal life 

 and then gradually increased up to hatch- 

 ing. 



Fink (iz) found that the carbon dioxide 

 output of potato beetles throughout the 

 progress of hibernation invariably indi- 

 cated a reduced metabolic activity, in 

 some respects comparable wih that of 

 starving animals. In the latter, how- 

 ever, "the velocity of reaction of the life 

 processes continues to function most 

 actively and reserve substances are rapidly 

 depleted, a condition eventually leading to 

 the death of the animal. In the [former] 

 most of the life activities are considerably 

 depressed and nutrient material is, there- 

 fore, used sparingly." With older beetles 

 the metabolic activities were also ex- 

 tremely reduced, but not to the extent met 

 with in hibernating or starving forms. 

 Fink (n) in another investigation used 

 the eggs and pupae of ten different species 

 of insects in his study of metabolic rates. 

 His experiments showed a greater amount 

 of energy change during embryonic de- 

 velopment as compared to the energy 

 developed during metamorphosis. This 

 was shown by the greater carbon dioxide 

 output and by the oxygen intake. Low 

 respiratory quotients were obtained during 

 the embryonic and pupal development of 

 insects, resembling similar low quotients 

 obtained with hibernating forms. 



Northrop (zo) made another study of 

 the metabolism and of the duration of life 

 of cultures of Drosofhila and found that 

 more carbon dioxide was given off at 

 i5°C. than at z6° or 30 , when both cul- 

 tures were in the dark, and that more 



carbon dioxide is evolved in light than in 

 darkness. This effect of light on carbon 

 dioxide production has been shown earlier 

 by Loeb (15) to be due to an increase in 

 muscular activity, since insect pupae were 

 not affected. Quite high light intensities 

 have no effect on the duration of life of 

 fruit flies, whereas numerous investigators 

 have shown that illumination markedly 

 increased the carbon dioxide production. 

 The duration of life does not seem to be 

 determined by the time required to pro- 

 duce a limited amount of carbon dioxide. 

 Perhaps the most useful compilation of 

 data on metabolism is to be found in 

 Krogh's (14) monograph on ' 'The Respira- 

 tory Exchange of Animals and Man." 

 This includes the results of several original 

 experiments on insect pupae, particularly 

 on chrysalides of the beetle, Tenebrio 

 molitor (13). 



THE METABOLISM OF DRAGON FLY NYMPHS 



In a previous paper (Z5) the writer 

 discussed in detail the effect of starvation, 

 darkness, and temperature upon the carbon 

 dioxide output of one of the dragon fly 

 nymphs, Aeshna umbrosa. The adult 

 dragon fly or "darning needle" is well 

 known to almost every one, but fewer 

 people are acquainted with the immature 

 stage, which spends this period of its life 

 cycle in the water, breathing by means of 

 rectal gills. These nymphs are easily ob- 

 tained and live successfully under general 

 laboratory conditions. They offer es- 

 pecially desirable material for the study 

 of respiration in a truly aquatic form. 

 The nymphs used in the study were col- 

 lected at the same time and from the same 

 creek and were all approximately the same 

 age. Three sets of ten insects each were 

 used in each type of experiment and the 

 results averaged and graphically shown. 



The apparatus used by the writer was 

 essentially the same as has been used by 



