Mar. 24,1923 
Temperature and Evaporation on Aphis pomi 
987 
Temperature, during periods when no other factor limits the rate of 
development of the species, constitutes a more satisfactory index than 
does the rate of atmospheric evaporation. 
The relation of temperature to the rate of development of Aphis pomi 
may be represented by a hyperbolic curve having the formula: length of 
developmentalperiodmday S - Temperatures ^ d( J° ees Fahr enheit- 4 r 
Plant growth frequently constitutes a factor limiting the rate of devel¬ 
opment of Aphis pomi feeding on slowly growing foliage. 
27976—23 - 5 
