64 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 1 



In this curve the thermal constant has been increased 25% for every 

 decrease of 10° from the optimum or with a uniform coefficient of 1.25. 

 Upon plotting this curve it is found that the thermal constant in- 

 creases uniformly toward the critical point, but that it would approach 

 the critical point to infinity. Upon plotting the curve of the coeffi- 

 cients of increase of velocity of such a curve, the curve H. C. of figure 

 2 is secured, which corresponds very closely with those secured from 

 actual observations. 



But if there be such an empirical temperature curve for each 

 species or phenomenon, it is evident that there can be no thermal 

 constant which will be constant at all temperatures, for it increases 

 in a uniform ratio below the optimum. A constant may however be 

 secured by reducing the increments of temperature for each unit of 

 time to terms of the thermal constant at the optimum, which is there- 

 fore 1. Thus the values of one unit of time on the hypothetical curve, 

 H. C, figure 1, would be 0.1 at 35°, the optimum, 0.056 at 25°, and 

 0.021 at 15°, etc. "When by adding these values sufficient are secured 

 to make 1, the thermal constant has been reached, equivalent to the 

 thermal constant at the optimum temperature. To secure such values 

 it would be necessary to secure the thermal constant at the optimum 

 and at two or three constant temperatures below, upon which the 

 curve of the species or phenomenon might be plotted and the values 

 for each degree of temperature for one unit of time calculated. 



At present this is, of course, largely a hypothesis, but it accords 

 with all the facts which have come under our observation, and seems 

 worthy of attention by those who are engaged in study of the relation 

 of temperature to insect life; for without hypotheses what could we 

 accomplish in such work? During the coming year we hope to defin- 

 itely determine this matter by rearing large numbers of two or three 

 common household pests in specially constructed apparatus which 

 will maintain constant temperatures, and thus enable us to secure 

 the thermal constants for various temperatures, which may then be 

 compared with the amount of temperature accumulated with varying 

 temperatures. 



It may seem to some that such studies are of rather remote impor- 

 tance to practical economic entomology, but as such work accumulates 

 it becomes more and more evident that a positive knowledge of these 

 fundamental factors governing the life of insects may have great 

 practical value, and that entomology, as well as all biological science, 

 must consider its relations to the more exact and fundamental sci- 

 ences of physics and chemistry, if we are to have exact knowledge of 

 the life with which we are dealing. Hunter and Hooker have re- 

 cently suggested the practical application of such work in their study 



