285 
slight influence. Our plan, therefore, was to make a study of our data 
with reference to temperature alone, and find as nearly as possible the 
temperature constant for each of the stages; then to study the data with 
reference to humidity and evaporation and ascertain what effects differ- 
ent humidities or different evaporation rates had on the temperature con- 
stant. Several statements have already been made to the effect that the 
influence of humidity and evaporation is too slight to make it necessary 
to take them into account. It remains now only to present the data upon 
which this conclusion was based. 
It is hardly to be expected that the degree of humidity of the atmos- 
phere or the rate of evaporation could have any effect on the larva, sur- 
rounded as it is by the juicy substance of the apple; therefore the data 
bearing upon the relation of these factors to the rate of larval develop- 
ment have not been brought together; but the data bearing upon their 
relation to the rate of development of the egg and pupa are summarized 
in the following tables (47-50). The ranges of temperature are given 
at the top of the tables and the ranges of humidity or the rate of evapora- 
tion in the first column at the left, and then, in their proper places, are 
inserted the average effective day-degrees of all the individuals whose 
periods were observed at the respective temperatures and humidities or 
rates of evaporation. 
In the right-hand column are given the average effective day-degrees 
for the different degrees of humidity or evaporation regardless of tem- 
perature; and at the bottom of the tables, the average effective day-de- 
grees for the different temperatures, regardless of humidity or evapora~ 
tion. The smaller figures, above the numbers indicating the average 
effective day-degrees, record the number of observations on which the 
averages are based. 
Tables 47-50 show that there is no consistent variation in the aver- 
age total effective day-degrees corresponding to the different degrees of 
humidity or rates of evaporation. The variations are rather hit and 
miss, apparently depending more upon the number of individuals upon 
which the averages were based than upon any other factor. In all cases 
where the number of observations on which the averages were based is 
large, the average effective day-degrees vary only slightly from the total 
average. Possibly there is some slight indication that incubation pro- 
ceeds at a greater rate at humidities between 70 and 74 than at higher or 
lower humidities and at rates of evaporation between 20 and 24 than at 
lower rates; but we are hardly warranted in basing any definite conclu- 
sion on this indication, and if we were, the variations are so slight that 
for practical purposes they could be disregarded, since the extreme 
variations where the number of observations from the average are 500 or 
more would amount to a variation of less than one eighth of a day in the 
period. 
Ee RRs eo oe Rene eee 
2 
