igio] Determining Optimums of Temperature and Moisture 153 



ture. Chart No. i, curve No. 4 shows that in our tests Toxoptera 

 graminum experiences the lowest mortality at 80° F., curve 

 No. 3 shows that the highest daily reproduction is at 80° F., 

 curve No. i shows that the shortest time from birth to maturity 

 occurs at 80° F., and curve No. 2 shows that the average period 

 of reproduction is only a little less at 80° F., than at 70° F. 



CHART ND. I 



100 



-5 



■eo. 



-55 



50 



NO. 1= NO OF DAYS FROM BIRTH TO MATURITY 

 N0.2= LENGTH OF REPRODUCTIVE PERIOD 

 N0.3= DAILY RATE OF REPRODUCTION 

 N0.4= MORTALITY 

 NO. 5= NO. OF YOUNG 



90T. 



TEMPERA' 



Chart No. 1. — Plotted data showing the relation of Toxoptera graminum 

 Rondani to temperature under constant relative humidity of 75°. In curves 

 No. 1 and No. 2, point at 50° F. represent the average of 6 individuals, at 70° 

 F. 27, and at 80° F. 28. In curves No. 3 and No. 5 point at 50° F. represents 

 the average of 6 individuals, at 70° F. 27, at 80° F. 28, and at 90° F. 201. In 

 curve No. 4 point at 50° F. represents the average of 54 individuals, at 70° F. 

 108, at 80° F. 57, and at 90° F. 201. 



Clearly, taking into consideration the effect of higher daily rate 

 and shorter period of immaturity on the geometric rate of increase, 

 T. graminum will under constant relative humidity of 75° produce 

 the maximum number of progeny in a given time at 80° F. It is, 

 therefore, reasonable to conclude that the optimum temperature 

 for T. graminum under 75° relative humidity is about 80° F., 

 possibly a little above or a little below. 



