general features of water exchanges 195 



"§ 73. Behavior 



Behavior toward aqueous environment shows extraordinary 

 variety ; everyone knows that some species of organisms stay in or 

 near water, others shun it. Those animals that have been care- 

 fully tested are able to find water more often than not ; even visual 

 accompaniments or gravitational features are used for its approxi- 

 mate detection. Other species (bee, fly, spider) sense water by 

 its humidity or its touch and make few mistakes in moving toward 

 it. Water vapor attracts rats, salamanders, wood lice, and some 

 beetles ; they frequent moist air still more when they are in water 

 deficit. Other species avoid air that is nearly saturated with mois- 

 ture {e.g., mealworm beetle). Conditioning is not found to play 

 much role in these preferences. Behavior appropriate for the per- 

 servation of water content varies among species from the highly 

 developed sensitivities and responses to water seen in mammals 

 and insects, to the small provision of sensorimotor capabilities in 

 amphibia and earthworms. But even the latter are far from indif- 

 ferent to water and water exchanges. 



"§i 74. Water contents and turnovers 



Animals are chiefly water. While that is widely recognized, 

 data that will allow quantitative comparisons among contents of 

 water are here shown (tables 18 and 19). This information can 

 be used {1) to transform body weights to volumes of water, where- 

 upon a number proportional to ± AW (AW being a fraction of 

 total substance (body weight) present) may be based on water 

 initially contained; (5) to relate water to non-aqueous materials, a 

 ratio especially desirable in those living units where absolute 

 weight or volume cannot be regularly and repeatedly measured; 

 (5) to indicate what deviations may be expected in the proportions 

 of water to non-aqueous materials. Further, it is widely believed 

 that some materials (such as fat) are unrelated to water content, 

 and hence they might be eliminated from consideration by subtract- 

 ing their weights from both the total and the dry weights. 



The specific gravities of the organisms listed vary from about 

 1.0 to 1.1. In this small range it is usually unnecessary, in view 

 of other inaccuracies, to convert weights to volumes, and vice versa. 



Variabilities of weight or volume in one individual maintained 

 in supposed water balance may be compared in a number of species 



