Feb. '08] JOURNAL OF ECONOMIC ENTOMOLOGY 65 



of the relation of temperature to the incubation of eggs of the cattle 

 tick and it seems probable that a similar application might be made 

 in determining the time of treatment of the codling moth, though it 

 is hardly probable that it will be necessary in the latter case. 



But it is upon a positive and not merely hypothetical knowledge 

 of such controlling forces as temperature that our science must rest 

 and no one can foresee what entirely practical application may be 

 made of it in the future study of new pests as they present themselves 

 for study under new conditions. 



The remainder of the proceedings of the 20th meeting of the Associ- 

 ation of Economic Entomologists will be given in the next number of 

 the Journal. It has been deemed advisable, in view of its close rela- 

 tion to two papers in this number, to publish at the same time Mr. 

 Hooker's summarized account of our knowledge of the role of ticks 

 in the transmission of disease. The paper was prepared originally for 

 presentation at the meeting and as a part of the symposium on ticks, 

 consequently it is very fitting that it should appear at this time. 



A REVIEW OF THE PRESENT KNOWLEDGE OF THE 



ROLE OF TICKS IN THE TRANSMISSION OF 



DISEASE* 



By W. A. Hooker, Bnrecm of Entomology, U. ^. Department of Agriculture. 



Not until within the last decade has the importance of insects and 

 related animals as agents in the transmission of disease been fully ap- 

 preciated. Within this period, however, the progress of our learning 

 has advanced at an astounding rate. It was but fifteen years ago that 

 Smith and Kilborne first demonstrated the role that the cattle tick, 

 Margaropus {=Boophilus) annulatus, plays in the transmission of 

 Splenetic or Texas Fever of Cattle, and only ten years ago that Ross 

 first employed Anopheles in his mosquito-malaria experiments. To- 

 day we all know of the mechanical and biological agency of the flies 

 and mosquitoes in the transmission of typhoid fever, cholera, anthrax 

 or eharbon, nagana or tsetse-fly disease, surra, malaria, yellow fever, 

 filiariasis and dengue, and of fleas in the transmision of bubonic 

 plague. Together and with the investigation of the Bacteriologist and 

 Protozoologist has come that of the Entomologist in the study of the 

 life history and habits of the disease-carrying injects. We are all ac- 

 quainted with the investigations in this country of Dr. L. 0. Howard, 



*Prepared for presentation at the meeting of the Association of Economic 

 Entomologists, held at Chicago, Illinois, Dec. 27-28, 1907. 



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