April, '10] SANDERSON : TEMPERATURE AND INSECT GROWTH 



133 



The effect of short 

 exposure to heat above 

 the point of heat-rigor 

 is well shown by the ex- 

 periments of Bellati 

 and Qua j at (3) in 

 which silk worm eggs 

 were maintained at con- 

 stant high temperatures 

 for a few seconds and 

 the subsequent mortal- 

 ity then noted. The 

 curves in figure 22 show 

 that the higher the tem- 

 perature the shorter the 

 time eggs may be ex- 

 posed to it, and al- 

 though the eggs may be 

 exposed to a lower tem- 

 perature for a much 

 longer time, if they re- 

 main at any tempera- 

 ture above that of heat- 

 rigor, they will die. 



The fact that metab- 

 olism continues at low 

 temperatures has been 

 shown by Merrifield 

 (18) in his experiments 

 with pupae of Eugonia 

 autuninaria and alni- 

 aria exposed to 2° and 

 0°C. respectively for 

 varying lengths of time 

 and then developed at 

 room temperature. As 

 shown in figure 23, the 

 pupa; of E. autuninaria 

 at 2°C. as the time for 

 emergence after they 

 were brought to normal 



20^ 30^C. -10° 0° 10° 20° 30° C- 



Days 



30 S- '■ 



70 



Fig. 24. Relation of temperature to the de- 

 velopment of Lt/siphlebiis tritici, A, and Toxoptera 

 grcDiiinum, B, according to Hunter and Glenn 

 (original). 



