Decembee 6, 1907] 



SCIENCE 



771 



riers of certain diseases of men and ani- 

 mals we realize that the discoveries of the 

 thirteen years under consideration have 

 been vital to the welfare of humanity, and 

 that possibly we are as yet only on the 

 threshold of discoveries which will prolong 

 life and will conduce to added happiness 

 of millions yet unborn. 



The ticks and the mosquitoes of the 

 genera Anopheles and Stegomyia, and 

 many other biting flies, fleas, the common 

 house fly, the bed bug and presumably 

 other insects, are now recognized not only 

 as nuisances, but as most serious menaces 

 to health, and measures for the control of 

 nearly all of them are becoming well under- 

 stood, and all of this has come about in 

 the past eight years. The enormous San 

 Jose scale literature referred to in the 

 preceding paragraph is exceeded by the 

 literature of this subject. Not only have 

 popular journals and scientific transactions 

 been filled with articles dealing with these 

 discoveries, but books have been written, 

 and medical journals have been crowded 

 with announcements of discoveries bearing 

 upon this line of investigation. 



Here, economic entomology has touched 

 a new side of human interest; it is the 

 health of man and not the preservation of 

 his property that is concerned, and the 

 interest has been a more vital one. The 

 prime investigators, it is true, have been 

 medical men, but the economic ento- 

 mologists have done their full and most 

 important share, and it has only been by 

 the combination of the labor of both classes 

 of workers, that the present results have 

 been achieved. 



In both of these last two developments 

 of this period— namely, the San Jose scale 

 work and the work against insects injuri- 

 ous to health, the whole world has been 

 vitally interested, and in another depart- 

 ment, which has reached the highest stage 

 during this time, many nations are becom- 



ing interested ; and that is the international 

 work with the parasitic, or predatory, in- 

 sect enemies of injurious insects. Orig- 

 inally suggested, and experimentally tried 

 on a small scale, but with scanty results, 

 very many years ago, the first successful 

 large scale experiment was concluded in 

 California about twenty years since, by the 

 work of an agent of the United States 

 Department of Agriculture, Mr. Albert 

 Koebele. Both the state of California 

 and the United States Department of 

 Agriculture have carried on the work since 

 that time, and they have been joined by 

 the territory of Hawaii, by the colony of 

 "Western Australia, by South Africa, by 

 the British West Indies, by Egypt, by 

 Portugal, by Italy, quite recently by 

 France, and at the present moment an 

 entomologist from Chile is in the United 

 States searching for beneficial insects to 

 take back with him to South America. 



All of this work was done on a rather 

 small scale, although occasionally with 

 excellent results, until three years ago, 

 when the effort to introduce the European 

 parasites of Ocneria dispar, known as the 

 gypsy moth, and of Porthetria chrysor- 

 rhea, known as the brown-tail moth, into 

 the United States was begun. In the 

 northeasterly portion of the United States, 

 both of these injurious insects introduced 

 accidentally had spread enormously, and 

 occurred in countless numbers. The per- 

 centage of parasitism from native Ameri- 

 can parasites was very small. The normal 

 percentage of parasitism in the native 

 homes of the injurious species was very 

 great. There seemed to be no object in 

 limiting the importations of parasites— the 

 greater the number introduced, the sooner, 

 it seemed, would success be reached ; there- 

 fore, from the start the work has been done 

 upon a very large scale. Hundreds of 

 thousands of host insects containing para- 

 sites have been brought each year from 



