August 21, 1908J 



SCIENCE 



227 



who is willing to pay the dues. The state- 

 ment has recently been made that this has 

 resulted in a membership which is largely 

 non-professional. Such a statement is 

 wholly misleading. While the fact that a 

 man is a member of the society is no guar- 

 antee that he is a trained chemist, there are 

 very few members who are not engaged in 

 chemical work and I think I am safe in 

 saying that ninety per cent, of the mem- 

 bers have had a good chemical training. 



The American Chemical Society is about 

 to establish a Journal of Industrial and 

 Engineering Chemistry. This journal, 

 too, is to be sent to all members of the 

 society. The objection has been raised that 

 it should be sent only to those members 

 who are especially interested in it. Such a 

 course does not seem wise for two reasons. 

 First, in accordance with the ideal of the 

 society, which is to care adequately for the 

 needs of all classes of chemists, we wish to 

 continue to furnish all of our members 

 with original papers as well as with ab- 

 stracts in all fields of chemistry. Second, 

 if we were to adopt the other plan, we 

 could afford to give as a rebate to any one 

 who does not care for the journal only the 

 amount which would be saved by printing 

 a smaller number of copies. This amount 

 is so small as to be scarcely an object. We 

 seem to be justified, therefore, in adopting 

 for the Industrial Journal the same plan 

 which has met with so much success in the 

 case of Chemical Abstracts. 



We already have some members in 

 nearly every civilized country in the 

 world— in England, Germany, South 

 Africa, Australia, New Zealand, China, 

 Japan, Chili, Brazil, Argentina and many 

 others. 



The broad policies which have been 

 adopted by our society can succeed only on 

 the basis of a very large membership. We 

 need the loyal support of every American 

 chemist. W. A. Notes 



THE THEORY OF THE PARASITIC CONTROL 

 OF INSECT PESTS 



All who have recently discussed the 

 question of the possibility of controlling 

 insect pests by the use of parasitic or 

 predaceous insects or by fungous or bac- 

 terial diseases, have failed to consider the 

 subject from a very important point of 

 view. 



The conditions determining the life or 

 death of insects are much more compli- 

 cated than is usually appreciated, and the 

 individual factors in the problem are far 

 from independent. The correct estimation 

 of this interdependence of the causes of 

 death in insects is of vital importance in 

 this connection. The efficiency of each 

 factor is so influenced by the efficiency of 

 the others that the elimination of one cause 

 of death or the addition of an entirely new 

 natural enemy will usually have but a 

 slight effect upon the rate of survival or 

 none at all. 



The reproductive powers of most organic 

 beings are very great. Were not all 

 creatures liable to die prematurely, that is, 

 before they reproduced themselves, repro- 

 duction would of necessity have been 

 limited to two offspring from each pair. 

 Whenever reproduction is at a more rapid 

 rate it is a prima facie evidence that the 

 chance of premature destruction requires 

 it and the greater the reproductive power 

 the higher this normal death rate. Were 

 conditions otherwise, rapid extinction or 

 enormous increase would result. The fact 

 that species maintain themselves for ages 

 with the ratio between the birth rate and 

 that of premature death not varying an ap- 

 preciated fraction of a per cent, is very 

 evident. 



This balance between birth- and death- 

 rates is much greater than the numerical 

 stability. For instance, in the case of a 

 species increasing a hundred fold in a gen- 

 eration, an average disturbance of only a 



