88 Causes of Emigrations 



substance and holding the water produced in metabolism" (Buxton, 

 1930) , A clothes moth (Tinea) can subsist throughout life on 

 nothing but air-dried wool or fur which contains from 3.66% to 

 9.08% of water, and maintains its body water at 57.66% to 59.83% 

 (Babcock, 1912) . The larva of the beetle Trogoderma, which is 

 commonly known as the "museum pest," has lived for more than 

 four years in a small bottle without food, at times molting and 

 devouring its own skin (Wodsedalek, 1917). Argasid ticks may 

 live two to six years as unfed adults, but ixodid ticks usually sur- 

 vive only for six to eight months (Nuttall, 1911) . 



"The length of time that animals can endure atmospheres of 

 low relative humidity in general depends primarily on the kind 

 of integument and secondly on the proportion of the surface to 

 body mass. Metabolism of an organism is important in its re- 

 sistance to exsiccation" (Hall, 1922) . A man when starved may 

 lose 40%. of his body weight, including half of his proteins and 

 nearly all of his glycogen and fat, without serious danger, but the 

 loss of 10% of his water results in serious disorders and of about 

 20% in death (Rountree, 1922). Shelford (1929) investigated 

 the effects of rapid evaporation produced by air currents, and 

 measured the rate by Livingston porous cups. "The animals killed 

 by rapid evaporation fall into two distinct groups: (a) those dying 

 with an evaporation varying from 0.07 to 5.40 cc, after an exposure 

 varying from 5 to 165 minutes, and (b) those dying with an 

 evaporation of 31.0 to 42.0 cc. after an exposure of 1,300 to 2,220 

 minutes. The first group was made up of soft skinned amphibians, 

 the second of chitin-covered arthropods. Even though the arthro- 

 pods were much smaller and hence had much more surface per 

 volume, they lived from 8 to 450 times as long as the amphibians." 

 Littleford, Keller, dC Phillips (1947) tested the ability of five species 

 of plethodontid salamanders to endure desiccation and found 

 that they lost 18 to 25.85% of body weight before death. Ability 

 to endure water loss was correlated with habit and habitat. The 



