130 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 3 



of temperature, as long as the temperature remains below the maxi- 

 mum A, will not kill the organism if it be returned to normal tem- 

 peratures, while it will die if maintained at a constant temperature 

 above W. Metabolism does not necessarily cease during heat-rigor at 

 temperatures above W, but is greatly retarded. 



If the temperature is lowered, then at a point K, cold-rigor sets in 

 and activity ceases. If it be cooled below freezing to a point T^, 

 termed the "critical point," the internal heat of the insect rebounds 

 to a point N,. But if the body temperature again falls below the 

 critical point, as at T3, then death ensues. If after the critical point 

 has been reached and the rebound occurs, the insect be removed to 

 normal temperatures, it will usually revive, depending upon the 

 length of time it has been under-cooled. As in heat-rigor, metabolism 

 does not cease at temperatures producing cold-rigor, though no activity 

 is apparent, but below a point Tg, all metabolism ceases. Death at 

 low temperatures is held to be due to molecular rearrangement and 

 mechanical injury, whereas death at high temperature is due to 

 chemical changes in the proteids. The relation of both excessive heat 

 and excessive cold is therefore seen to depend upon the time involved 

 and the rapidity with which the organism is cooled or heated and 

 Avitli which it is subsequently brought back to normal temperatures. 



This, very briefly, is my understanding of Bacluuet Jew's views which 

 he supports by the citation of the whole literature bearing on the 

 subject. 



In his Experimental Morphology Davenport brought out the same 

 facts as regards both plants and animals, but uses a slightly different 

 terminology. The point at which metabolism ceases at high tem- 

 peratures is termed the maximum, and at which death is immediate, 

 the ultra-maximum, and likewise, the point at which metabolism ceases 

 with low temperature is called the minimum, and the "critical point" 

 of Bachmetjew upon the maintenance of wdiich death ensues, is called 

 the ultra-minimum. This term is preferable to that of "critical 

 point," for both minimum, optimum, and maximum are critical points 

 in the relation of temperature to the life of the organism, and the term 

 has been so differently used by different groups of workers and by 

 different sciences that it lacks definiteness. The temperature below 

 which cold-rigor ensues is often termed the "minimum temperature 

 for activity" or growth, or germination, but as the true minimum is 

 somewhat below this, we may better term it the point of cold-rigor, 

 and the temperature at which heat-rigor commences the point of 

 heat-rigor, the latter also being below the real maximum. 



