264 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 14 



THE RESPONSE OF THE BEAN WEEVIL TO DIFFERENT 

 PERCENTAGES OF ATMOSPHERIC MOISTUREi 



By Thomas J. Headlee, Ph.D., New Brunswick, N. J. 



Since the publication of "Some facts relative to the influence of at- 

 mospheric humidity on insect metabolism"^ the writer has, as time 

 would pennit, collected data on the response of the bean weevil, Bru- 

 chus obtectus, to varying degrees of atmospheric moisture ranging in 

 stages from less then 1% to approximately 100%. He has now com- 

 pleted three distinct sets of experiments and the curves, which are pre- 

 sented, have been constructed on the basis of the average of the ex- 

 periments. 



As in his previous experiments of this sort the utmost care has been 

 taken to eliminate variable factors other than atmospheric moisture. 

 The insects have been kept throughout their life cycle in darkness and 

 and they have been subjected to a constant temperature of 80° Fahr., 

 which did not vary as much as a degree either way. The pull of the 

 water pumps has been approximately sufficient to counteract the 

 changes in barometric pressure. 



In each set of experiments the adult weevils were taken from exact- 

 ly the same sources. 



In each of the three series of experiments five containers were em- 

 ployed for each selected percentum of atmospheric moisttire. Each 

 of the five containers received twenty-five adult beetles as nearly even- 

 ly divided between the sexes as was practicable. Thus each selected 

 percentum of atmospheric moisture in each of the three sets of expe- 

 riments started with one hundred and twenty-five (125) adult weevils. 

 The succeeding progeny in the five containers ranged from nothing in 

 very low atmospheric moistures to over 1200 individuals in more fav- 

 orable atmospheric moistures. The factor of individual variation in 

 response was in this way reduced to the lowest practicable minimum. 



The means employed to condition the atmosphere has not, it is 

 thought, been heretofore considered in a formal way. The air was tak- 

 en from outside of the building and led through a rubber pipe to a con- 

 centrated sulphuric acid drier. From thence the air stream was led 

 into a distributing bottle from which each of the lines for the particu- 

 lar selected percentum of atmospheric moisture took their rise. One 

 line led directly into an experimental chamber which was held at a 

 constant temperature of 80° Fahr., and passed directly through the 

 group of five containers in which the beetles and later their progeny 



'Paper 17 of the Technical Series, N. J. Agricultural Experiment Stations, Depart- 

 ment of Entomology. 



'Journal of Economic Entomology, Vol. X, No.l, 1917. 



