June, '22] 



GLENN: CODLING MOTH AND TEMPERATURE 



195 



degrees on account of temperatures above 88 deg. twice the day-degrees 

 above 88 were subtracted from the day-degrees above 50. This gave 

 the effective day-degrees recorded in column 5. Multiplying the day- 

 degrees in column 5 by the periods in column 2, we get the sums of day- 

 degrees, or the total day-degrees, recorded in column 7, which are quite 

 uniform for all temperatures. 



Proceeding with the data on the larval period as we did with the 

 data on the incubation period, we find that if twice the number of 

 day-degrees above 85 be subtracted from the day-degrees above 50, 

 we shall have temperature factors in column 5, which when multi- 

 plied by the periods in column 2, give products which are fairly uni- 

 form in size. The number of larvae obser\^ed was com-paratively small, 

 being only 344, and the wider variation in the products as compared with 

 the products in the table of data on the incubation period is due to this 

 fact. It is generally true that the greater the number of observations 

 the more nearly does the average of the products approach a constant. 



.>^»<^o«--./B«r y../n.,-»<r Thc abovB tablc Is bascd 



TABL B 3 . TEMPeR/^TURB A NO THE , . ^ ^ , _ 



PI/PAL PSRIoa OF THE COOllNC-MOTH- upon observations on 3817 



pupae. To secure tem_per- 

 ature factors for the pupal 

 stage which when multiplied 

 by the periods would give 

 nearly the same results for 

 a 1 1 temperatures, it was 

 necessary to subtract twice 

 the day-degrees above 87 

 degrees from the day-de- 

 grees above 52 degrees. 



We concluded there- 

 fore, that the threshold of 

 development for the 

 egg and larva is approximately 50 deg. Fahr. and for the pupa ap- 

 proximately 52 deg. Fahr., and the degree of the m_aximum rate of de- 

 velopment for the egg is about 88 deg. Fahr., for the larva 85 deg. 

 Fahr., and for the pupa 87 deg. Fahr., that the effective day-degrees 

 for any day may be found by subtracting twice the day-degrees above 

 the degree of the maximum rate of development from the day-degrees 

 above the threshold of development, and that the sum of the daily day- 

 degrees for all the days in the period will be the theoretical thermal 

 constant. This constant in the case of the incubation period is about 

 163, the larval period 673, and the pupal period 241, (265 if 50 deg. 



