32 



JOURNAL OF ECONOMIC ENTOMOLOGY 



[Vol. 10 



rate of which was one liter in eight minutes or less. Barometric 

 pressure was the only variable against which no fairly complete meas- 

 ures were taken. In so far as possible the influence of this variable 

 was annulled by running the experiments simultaneously. 



The first phase of the investigation was concerned with the effect 

 of atmospheric humidity on late larval and the pupal stages and 

 included the responses of both the bean weevil and the Angoumois 

 grain moth {Sitotroga cerealella Oliv.). 



Table Showing the Effect of Atmospheric Moisture on Rate of Development of the Late Larval and Pupal 

 Stages of the Angoumois Grain Moth and the Bean Weevil 



Chamber 



Temp. 



Atmospheric 

 moisture 



Date of 

 beginning 



Emergence 



No. of days 

 in period 



No. of days 

 to maximum 



No. of 

 specimens 



Angoumois grain moth 



Bean Weevil 



It is here unmistakably shown that the speed of metabolism in the 

 pupa is increased, the period beijQg shortened in case of the moth from 

 17 days in 100 per cent to 12 days in 21.8 per cent and in the case of the 

 weevil from 22 days in 100 per cent to 14 days in 44.6 per cent. 



The next phase considered was length of adult life which in all 

 probability may be taken as a measure of the speed of adult metab- 

 olism. 



In the moth the length of the period was shortened by a decrease 

 in atmospheric humidity varying from 18 days at 100 per cent to 15 

 at 44.7 per cent and below. In the weevil, on the other hand, the 

 period as a whole was apparently but little affected. When, however, 

 period to maximum death is examined it becomes plain that the life 

 of the adult weevil was prolonged by a decrease in humidity as shown 

 by the increase of the period from 3 days in 100 per cent to 12 in 44.6 

 per cent and below. 



