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ILLINOIS ACADEMY OF SCIENCE 



the length of the stages ten or more per cent as com- 

 pared with the constant temperature of the same nu- 

 merical value (see Figure 4 B). Another very interest- 

 ing result of the experimental work is the demonstration 

 of the fact that the so-called threshold of development for 

 temperature which is the temperature just above which 

 development begins, differs under wet and dry conditions 



"F 10 ^0 10 ^T 



Fig. 4A and 4B. Shown the effects of variability on human effi- 

 ciency and insect metabolism. 



(a) Curve A shows the effect of changes of temperature on the 

 efficiency of 300 men in a Connecticut factory. The center indicates 

 no change in temperature from the preceding day. At the right are 

 shown rises of temperature and to the left fall in temperature in de- 

 grees. In general variability favors efficiency. Curve B shows the 

 same for students but decrease in efficiency with rise in temperatures 

 which exceed 5° are evident (after Huntington). 



(b) Is a curve showing the effect on the length of the pupal stage 

 of the codlin moth of a daily rise in temperature indicted by the scale. 

 The vertical scale gives the per cent deviation from a constant tempera- 

 ture with the different amounts of increase. 



