208 



ANALYSIS OF THE ENVIRONMENT 



extend along a humidity axis, as does that 

 of humid Batavia in Java. The range both 

 in temperature and in humidity is fre- 

 quently much less than that shown for 

 Jhansi and Simla with their monsoon cli- 

 mates. 



Tropical climates, if they show seasonal 

 differences at all, have the main seasons 

 determined by moisture relations. Such 



main variation along the temperature axis. 

 Human death and insect mortality are 

 among the important phenomena that may 

 well be affected by temperature and humid- 

 ity (Huntington, 1919). Eggs of the desert 

 locust (Schistocerca gregaria) have a much 

 more restricted temperature tolerance at 20 

 per cent relative humidity than at complete 

 saturation (Fig. 49). 



TENTATIVE 

 DISCOMFORT SCALE 



, Usually 

 Uncomfortable 



I Often 

 . f Uncomfortable 



40 50 60 70 80 90 



RELATIVE HUMIDITY IN PER CENT 

 Fig. 48. Temperature-humidity graphs of some important climatic types. The shaded fig- 

 ure shows the composite climate of twelve large cities inhabited mainly by white people. 

 (Simplified from Taylor.) 



climates are in striking contrast with those 

 of coastal regions in the temperate latitudes, 

 as illustrated by Seattle and still more so 

 with a continental climate such as exists in 

 Winnipeg. Apes and monkeys characteris- 

 tically live in warm climates where the 

 seasonal differences in rainfall or humidity, 

 or both, may be large; the white man 

 thrive? best in temperate chmates with the 



Extensive studies of the rate of develop- 

 ment and of mortahty of the codling moth 

 (Carpocapsa pomonella) and the chinch 

 bug (Blissus leucopterus) similarly have re- 

 duced ranges of temperature tolerance with 

 lower relative humidity (Shelford, 1927, 

 1932). Many insects have an optimum 

 combination of temperature and humidity, 

 both for survival and for development. Of- 



