June, '17] FREEBORN: RICE FIELDS AND MALARIA 357 



These two mosquitoes breed in the rice fields close to the contour 

 checks which wind about through the fields to hold the water at the 

 difi"erent levels, their abundance depending largely on the character of 

 the rice stand. A heavy and uniform stand of rice, growing well up 

 to the checks, produces relatively few mosquitoes while a sparse stand 

 with irregular growth at the checks generally breeds anophelines in 

 large numbers. Far more important than the rice fields proper, how- 

 ever, are the overflow pools of surplus water. These vary in size from 

 small wayside pools to vast water-soaked sloughs that lack the natural 

 drainage to keep them dry. These bodies of water, both large and 

 small, breed enormous numbers of mosquitoes and are entirely un- 

 necessary. Careful construction of the irrigation ditches together with 

 an intelligent and economical use of water would entirely eliminate 

 them in a majority of cases. 



The irrigation of the rice fields does not begin until May. The 

 mosquitoes, however, begin active breeding in March and April, 

 utilizing neglected pools of standing water. Again after the water is 

 drawn from the rice fields in October, the mosquitoes continue to 

 breed actively until the latter part of November, again utilizing neg- 

 lected and useless pools. If, therefore, all possible breeding pools 

 could be controlled before and after the rice season as well as the out- 

 side pools that occur as results of rice cultivation during the season, 

 the mosquito population would be so considerably reduced that the 

 number breeding in the rice fields proper w^ould be almost negligible. 



The best agricultural methods demand that the land used for rice 

 and the adjacent territory be as nearly dry as possible before the crop 

 is planted. Again the irrigating water should be on the fields only 

 just long enough to mature the crop. As the rice approaches maturity 

 every detail should be undertaken to ensure immediate drainage 

 away from the fields at the moment that the crop matures. The fields 

 should then remain dry until they are naturally irrigated by the winter 

 rains. Thus it will be seen that optimum agricultural methods coin- 

 cide with optimum mosquito control measures and w^hen the industry 

 has become scientifically standardized the mosquito question will be 

 controlled automatically to a large extent. 



Unfortunately, a large percentage of the rice cultivation is carried 

 on by tenant farmers whose only vision is to reap the speediest and 

 most lucrative returns. The result has been as might be expected, 

 the irrigation ditches are badly maintained, the land is robbed of its 

 chemical constituents by poor agricultural methods and the profligate 

 use of water. Perhaps the most striking phase is the living conditions 

 of the workmen. The labor is transient and many of the shelters are 

 mere shacks lacking any attempt to exclude mosquitoes with the result 



