118 



JOURNAL OF ECONOMIC ENTOMOLOGY 



[Vol. 3 



This will be seen to be generally true for the insects cited, as it has 

 been found for most animals and plants so far studied which live at 

 normal temperatures.^ 



lO--^ 



Days 



30 



30° C. 



10° 



20° 



30° C. 



Fig. 10. Relation of temperature to egg and pupal periods of Tenebrio 

 molitor (original). 



The eggs of the brown- tail moth, Eiiproctis chrysorrho^a, were placed 

 at the same temperatures and their curve is shown in figure 8. They 

 also failed to hatch at 10° and 12°C. and also at 32°C., showing that 

 the latter is above the optimum for a constant temperature. In this 



^The coefficient or index of the velocity or rate of growth or activity is 

 usually expressed in terms of the difference between two temperatures 10 °C. 



Rate at T„ + 10 



apart, and is expresf>ed by the formula - 



, in which the rate 



Rate at T„ 



is the rate of activity or time of growth at the given temperature, T„. To 

 determine the coefficient between any given tempei-atures with given rates we 



have the formula — R-'tte at Tn — y12_, in which X is the difference in tem- 



Rate at T„ + X '^ X 

 perature between the two points. Thus if the pupa transforms in twenty days 



at 20°C. and in ten davs at 30°C. the coefficient of velocity is _-X— -=2. 



10 10 



