230 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 7 



holism has been the decrease in the length of the instars. Other 

 indices of rate of nietabolism in common use are: (a) the amount of 

 carbon dioxide produced, (b) amount of oxygen consumed, (c) heat 

 produced by the organism, (d) for aquatic animals susceptibility to 

 weak cyanide has been shown to be an excellent method (Child*). 

 Those organisms and parts which have the highest rate of metabolism 

 go to pieces quickest. This method gives results exactly similar 

 to that of the measure of the carbon dioxide with which it has been 

 compared. Another method consists in measuring (e) the vigor of 

 the behavior reaction (Allee^) which has been found to compare favor- 

 ably with the cyanide results and measure of carbon dioxide. Thus 

 animals with a high rate of metabolism are more sensitive to stimuli 

 and react more vigorously than animals with a low rate. The study 

 of reactions to measured physical factors can no doubt be used to 

 advantage in the study of conditions affecting the organisms. 



In a series of experiments the writer^ has established gradients 

 of evaporating power of air by passing air of three different kinds 

 (rates of evaporation) across the respective thirds of a long narrow 

 cage. These experiments showed that frogs, salamanders, toads, in- 

 sects and milhpedes are sensitive to variations in evaporating power, 

 and turn back when they encounter air of an evaporating power 

 greater or less than their optimum. The experiments also showed 

 that after the animals had been in dry air long enough to have a 

 small amount of water withdrawn, they became more sensitive to 

 the effect of evaporation. The work on insects was not carried far 

 by the writer but additional experiments by E. 0. Deere and J. R. 

 Watson support the original results. 



In general the reactions were similar for comparable rates of evap- 

 oration no matter whether the evaporation was due to dryness, tem- 

 perature, or rate of flow. Furthermore, death was produced with the 

 same symptoms regardless of the cause of evaporation. There was 

 usually a period of excitation following a short exposure and a period 

 of depression, followed by death. The same disturbances which 

 cause animals to turn Ijack upon encountering air of high evap- 

 orating power result in modification of sensitiveness and in death if 

 it is continued and intensified. These three means of influencing 

 organisms are not to be regarded as independent of one another or 

 essentially different because all result from interference with the 

 internal life mechanism. The different results are dependent upon 



4R0UX Archives, XXXV, pp. .598-641. 



Uour. Expt. Zool., Vol. 13, p. 269-.344. 



6 Biological Bulletin, Vol. XXV, p. 79, with good bibliogi-aphy. 



