Proceedings of Eighth Annual Meeting 85 



ment of environmental conditions affecting density, disease transmis- 

 sion, etc. 



An important factor has been the hearty co-operation of the Max- 

 well-Yerger Corporation, which has unreservedly placed at the ser- 

 vice of the Government the facilities of a large plantation most 

 suitably situated for the pwrpose. 



The preliminary work thus far has been rather in the nature of a 

 survey, in which every promising clue was followed, or is being 

 followed, as far as the available means permit. The work, for the 

 time being at least, is not looked upon as a demonstration in the 

 sense of determining a method of malaria control suitable to this 

 particular section, but as an intensive investigation having for its 

 objective the study of mosquitoes that convey the disease and the 

 ascertainment of all facts or information useful in the better appli- 

 cation of known methods, or the development of new methods and 

 measures, to place malaria prevention upon a strictly economic 

 basis. 



The topography of the Mound area opposite Vicksburg is of 

 special interest in connection with malaria investigations. The sec- 

 tion has been admirably surveyed by the U. S. Geological Survey and 

 all the essential facts are a matter of convenient record. The loca- 

 tion of every house has been indicated on a large-scale map in its 

 relation to more or less predisposing conditions, and the whole ter- 

 ritory, of some thirty thousand acres, has been divided into four 

 sections presenting special features, which are being studied. 



Some twenty-five species of mosquitoes have been determined for 

 this section, the prevailing anophelene varieties being the quadri- 

 maculatus, the punctipennis, and the crucians. The quadrimaculatus 

 is the main source of malaria in this region but the actual degree of 

 infection has not been determined. The record card adopted both 

 for mosquito and malaria occurrence seems well adapted to the 

 purpose. The tentative results show the monthly distribution of the 

 different species of mosquitoes as ascertained by the usual method 

 but with the important addition that the amount of time required 

 for catching purposes is indicated. This would naturally show a 

 wide range during a period of years and according to the conditions 

 under which the catch was made. All conclusions based upon such 

 statistics must for the time being be looked upon only as suggestive 

 of the direction in which such inquiries are likely to be most use- 

 ful. But considering the Anopheles collected during 1919, certain 

 facts may be stated as follows : 



