33 



seepage puddles and natural drainage ditches. For 1 mosquito 

 produced by the rice ticlds the puddle produces 5 and the ditch 44. 

 The larval food-supply is evidently not responsible for this great 

 discrepancy in numbers of larvae, as it is evenly distributed throughout, 

 and the discrepancy is not, or only to a very minor degree, due to 

 the activity of larval enemies, because these are most numerous where 

 the larvae are most abundant, and vice versa. The seepage puddles 

 repeated on a larger scale the fluctuations of the rice fields in numbers 

 of larvae, food content, and number of enemies, but this was not 

 true of the ditches. 



The most noticeable difference between the rice fields and the ditches 

 was the heavy growth of blue-green algae and the presence of surface 

 films on the former, the films being absent and the blue-green algae 

 not abundant on the latter. These films do not occur in the Arkansas 

 rice fields, where mosquito lar\"ae are moderately abundant, and green 

 algae predominate there, the normal growth not being very heavy. 

 Rain is frequent during the rice season in Arkansas, but usually absent 

 in California. 



Consequently, the natural mechanism of control in the California 

 rice fields seems to be concerned, in part at least, with the general 

 condition of stagnation, the large amount of blue-green algae, and the 

 biological surface films. The last two of these conditions, however, 

 which prevailed on the rice fields from about 20th July to the latter 

 part of September, fail to account for the negative results obtained 

 during June and part of July. 



It appears out of the question to control mosquito production in 

 natural, uncared-for waters b}' attempting to diminish the larval food 

 supply, or by the introduction of natural enemies, except perhaps 

 certain fish. 



Further investigation in cfifterent parts of the State, to check the 

 negative results obtained from California rice fields, is desirable, and 

 it is also recommended that studies should be made of the biological, 

 chemical and physical conditions that obtain in a field where breeding 

 does not take place, to determine, if possible, the reason for such 

 negative results. 



In collections of adult mosquitos. Anopheles quadrimaculatiis 

 occidentalis (thought to be an efficient vector of malaria) was the 

 most numerous. It was present throughout the year, and very abundant 

 in August and September. Males probably clo not live through the 

 winter, as none were found from 19th 'November to 27th April. 

 A. pseudopiinctipennis also occurred, as well as a few Culicines. 



\\'oo (S. :\I.). Famine and Typhus Fever in China : A Simple Delousing 



Building. — Cliina Med. Jl., S/uini(Iiai, xxxiv, no. 5, September 

 1920, pp. 572-574, 1 fig. [Received 3rd December 1920.] 



In view of the fact that an epidemic of typhus may be expected 

 to occur during the next few months in the famine-stricken provinces 

 of China where typhus is endemic, a form of delousing station for 

 construction in or near the hospital compound is described. A small 

 box-shaped mud or brick building should be made, with gas-proof 

 walls and one small door opening outwards, with a capacity of 1 ,000 or 

 2,000 cu. ft. and a height of not over 7 ft. The clothes to be disinfected 

 should be hung on wooden poles laid across the room about 6 in. below 

 the ceiling and 1 ft. apart. 



The usual methods of disinfection with sulphur or with hydrocyanic 

 acid gas are described. 



