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ILLINOIS ACADEMY OP SCIENCE 



perature and evaporation, and temperature and air move- 

 ment. 



Light influences the length of the codlin moth pupal 

 stages as much as ten per cent. Evaporation differences 

 may cause the length of the pupal stage to be doubled 

 under certain conditions and the effects of air movement 

 are often similar. Variability of temperature shortens 



100 % 



Fig. 2. A climograph or temperature-humidity graph for man 

 and for two years at Urbana, 111. Horizontal distance represents hu- 

 midity; vertical temperature in Fahrenheit. The heavy curve with 

 lettered angles connects the following: a, temperature and humidity 

 comfortable for men lightly clothed and making no exertion; b, the 

 same when exercising; c, the lowest death rate; d, high eflBciency for 

 factory workers in summer; e, the same in spring and' fall; f, the same 

 in winter. The light curve with crosses inside of circles at the angles 

 and numbers adjacent connects the points representing the mean 

 monthly temperature and humidity at Urbana, 111., for the year 1897 in 

 which the chinch bugs did damage at Urbana and in which the death- 

 rate was high in Chicago. The numbers refer to months. The similar 

 curve with crosses at the angles is for the year 1891 in which there 

 was no chinch bug damage in Champaign county and the death-rate 

 was low in Chicago. 



