268 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 14 



smooth to give a pretty accurate idea of the effects of the different 

 percentages of atmospheric humidity on the rate of developmont of 

 this insect. 



As the next step in this investigation, it is proposed to evaluate the 

 retarding and accelerating effect of certain of these salts and to check 

 the measuring stick used in these sets of experiments by the carbon 

 dioxide index. 



Mr. R. N. Chapman: I should like to ask Mr. Headlee about the 

 moisture content of the beans. In trying some experiments with the 

 bean we found that the bean seemed to act as a buffei medium. The 

 bean would have to come into equilibrium with the vapor tension of the 

 air and the larvae would come into equilibrium with the moisture con- 

 tent of the bean. The moisture content of the bean would depend up 

 on how many larvae there were present. While in a general way you 

 get this effect which shows very nicely in these curves, in any particu- 

 lar instance you couldn't be sure of what would happen because it de- 

 pended upon the number of larvae that happened to be present in the 

 particular bean. Therefore, I have resorted to some insects which 

 lived free in food like many of those working in stored food products. 

 Before the larvae enter the bean they are pretty small, and when they 

 are exposed to the lower percentage of humidity the death rate is very 

 high. I presume you found the same thing. 



Mr. T. J. Headlee: I attempted to meet the variables you men- 

 tion by using large numbers of insects and averaging results. Inas- 

 much as the three extensive series seemed to agree among themselves 

 I felt that we were not very far off in spite of the difficulties which you 

 have mentioned. 



Mr. R. N. Chapman: Your curve shows that your results check 

 very nicely. That is the best proof. 



I should also like to ask yDu a question about your saturated solu- 

 tions of salt. When we tried them out with small volumes of air they 

 seemed to work very nicely. Then we tried them with larger volumes, 

 using a combination pressure and volume blower which would give us 

 a displacement of about sixteen inches of water, and we tried to run 

 through about two hundred cubic feet of air, we found that we couldn't 

 do it. Of course, I presume the whole secret of it is that up to a 

 certain point the ratio of air to moisture and the fineness into which 

 you can divide your air to pass it through is going to control the rate 

 at which the air and moisture come into equilibrium. 



Mr. T. J. Headlee: Your explanation seems reasonable. 



