358 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 10 



that infected laborers rapidly spread their infection throughout the 

 district by means of the numerous mosquitoes. 



The control of those mosquitoes that breed in the rice fields proper is 

 an extremety difficult matter. Larvicides that are efficient in mos- 

 quito control, such as oil, salt, etc., are detrimental to the rice. Fish 

 are not successful owing to the difficulty in keeping the fields stocked 

 and their inabilit}' to feed in the shallow water inhabited bj^ the mos- 

 quitoes. Dragonflies as adults may be looked upon as a check but 

 not as a control. The dragonfly larvae, even in the presence of an 

 abundant supply of mosquito larvse and pupse, prefer cannabalism. 



Theoretically, malaria can be controlled in two ways. If everyone 

 in a malarial district could be cured by means of quinine treatment the 

 mosquitoes would have no point at which to become infected or if 

 everj^one would take a daily prophylactic dose of quinine, the chances 

 of infection even though bitten by an infected mosquito would be 

 materially lessened and the death of the last infected mosquito would 

 see the community free from malaria. Secondly, if all malaria-bear- 

 ing mosquitoes were eliminated there would remain no transmitting 

 agency to convey the disease from the sick to the well and again 

 malaria would disappear from the community with the recovery of the 

 cases infected at the time of the elimination. 



Experience in different lines of preventive medicine points out the 

 difficulty of administration of universal quinine treatment. In this 

 country of personal liberty it would be practically impossible to force 

 any such measure upon the people no matter how beneficial it might 

 eventually be. On the other hand, those who have had experience with 

 anti-mosquito campaigns know the difficulties attendant to nominal 

 control, to say nothing of the elimination of mosquitoes from any given 

 district. 



The logical control of malaria in the rice districts of California rests 

 in the careful application of a combination of these two methods, — 

 zealous anti-mosquito campaigns together with careful quinine treat- 

 ment or prophylaxis. 



1. The rice field becomes an economic factor in the control of ma- 

 laria in endemic localities when they offer breeding grounds to large 

 numbers of anopheline mosquitoes that are capable of transmitting 

 the malaria parasites. This is true in the California rice fields. 



2. The pools of standing water outside the rice fields proper, but 

 owing their existence to faulty agricultural methods of the rice grow- 

 ers, are far more important than the rice fields proper. 



3. The control of breeding places outside the rice fields before, after 

 and during the rice season combined with an application of those 

 methods of rice cultivation that are recognized as agriculturally sound 

 w^uld substantially control the mosquitoes. 



