Mar. 30,1916 Temperature and Humidity and Insect Development 1187 
of humidity. Because of the difficulty of computing this zero, the writer 
has been requested to 
describe his method 
of computing effective 
temperatures. 
The first step is to 
tabulate all records of 
a given mean percent¬ 
age of humidity on a 
single sheet. The zone 
of effective tempera¬ 
tures must be worked 
out separately at each 
degree of humidity. 
Only by a laborious 
series of testings can 
the first zero be ap¬ 
proximated, unless the 
worker finds it by a 
fortunate chance. 
The total effective 
temperature is the cri¬ 
terion by which we 
finally know when we 
have rightly defined 
the limits of the zero. 
This is known as the 
thermal constant and 
is the multiple of the 
mean of the effective 
temperatures (be¬ 
tween the zero and 
the absolute), figured 
in day units, by the 
time in which these 
effective temperatures 
were experienced. 
Noneffective temper¬ 
atures, whether high 
or low, and the time 
in which they were 
experienced must be 
eliminated. The 
zone of effective tern- 
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Fig. 3 .—Graph showing the method ol determining the zone of 
effective temperatures at a humidity of $6 per cent. 
peratures will be finally reached for any given humidity when the 
