April, '10] SANDERSON : TEMPERATURE AND INSECT GROWTH 



117 



of growth, if there be no "thermal constant" {physiological constant 

 of Merriam) as far as a mere accumulation of temperatures is con- 

 cerned, and if the velocity of reaction varies according to the range 

 of temperatures; what then is the relation of temperature to the 

 phenomena of insect growth and how may we express it in numerical 

 terms ? 



To answer this question we must first have facts and then seek an 

 explanation. During the past year we have reared different stages 

 of several insects at fairly constant temperatures. Large numbers 

 of most of the insects have been employed so as to secure fairly 

 accurate averages. Ordinary bacteriological incubators were used for 

 temperatures of 80° and 90°F. An un-iced refrigerator maintained 

 a fairly constant temperature of about 65°F. in winter and 70°F. in 



20° 30^ c. 



20° 30° C. 



Days 



Relation of temperature to the period of incubation of eggs. 

 Fig. 8. Euproctis' chri/sorrhaa. Fig. 9. 8ain ia cecropia, ovigmal. 



summer. A constant temperature apparatus in which the cold from 

 an ice chamber was balanced by the heat from a gas jet and controlled 

 by an electric thermostat gave close to 60°F. and an ordinary refrig- 

 erator was iced so as to maintain approximately 50°F. The details 

 of the work involving a large amount of labor were carried on by 

 Mr. and Mrs. C. F. Jackson,, to whom the writer is greatly indebted 

 for the results. 



Only an outline of the results will now be given, the details of the 

 experiments being published later. The pupge of Malacosoma ameri- 

 cana, figure 7, were transferred to six different temperatures upon 

 pupation and the emergence of the moths noted. At from 16° to 

 32° C. they emerged in the time shown by the curve, but at 10° and 

 12° C. all died. It will be noted that from 20° to 30° C. the coefficient 

 of velocity is practically 2, while below 20° it increases very rapidly. 



