155 



(^URRENT NOTES. 



In the 'Annals o£ Tropical Medicine and Parasitology/ vol. iii, no. 5, 

 Mr. F. C. AVillcocks gives some interesting preliminary notes on the preva- 

 lence and habits of mosquitoes in Cairo and its environs. He comments on 

 the comparative rarity of malaria in Egypt, in spite of the extreme abundance 

 of the Anopheline, CelUa pharoensis, Theob., and tentatively suggests that 

 perhaj)s this mosquito is not really a carrier of malaria ; a view for which 

 there appears to be some justification. The only other Anopheline mentioned 

 as occurring in the area dealt with is a new species of Pyretopliorus, and it is 

 possible that this much scarcer species may eventually prove to be responsible 

 for such malaria as exists. The larvse of this Pyretopliorus were found in 

 brackish waters, and flourished in large numbers in the presence of 2*56 to 

 3*25 per cent, of common salt ; though even 1 per cent, of salt proved 

 eventually fatal to the larvae of Cellia, In this connection it may be inter- 

 estino' to recall that in Southern Nigeria Dr. W. M. Graham has observed 

 that the larvae of Pyretopliorus costalis^ Loew, can be destroyed by an addition 

 of 3 per cent, of common salt to the water in which they live, the salt causing 

 the disintegration and precipitation of the motile algse upon which the larvae 

 feed (Bull. Ent. Res. part i, p. 51). 



In the same publication as the foregoing, Sir Rubert Boyce, F.R.S., and 

 Mr. F. C. Lewis give a short account of some useful experiments which were 

 made for the purpose of testing the validity of the contention that the presence 

 of mosquito larvae in drinking water was beneficial ; this idea being based 

 upon the assumption that these larvae feed largely on bacteria, and would 

 therefore tend to eliminate pathogenic forms. The results obtained by the 

 authors by no means support these conclusions, for as they say : — " From 

 these experiments, it will be seen that in clean drinking water^ drawn from 

 the tap and exposed to the air, there is a slight multiplication of the number 

 of bacteria for a few days, and that then the bacteria rapidly decrease, in all 

 probability owing to the want of food material. If, however, living larvae 

 are placed in the water, there is a very rapid rise in the number of bacteria 

 per c.c, which is enormously increased if a larva happens to die. In other 

 words, larvae add something to the water, probably mucus, which acts as food 

 material, and which therefore increases the rate of development of the 

 bacteria, and a dead larva in decomposing still further increases the bacterial 

 proportion. In the case where typhoid bacilli were added to the water, the 

 presence of the larvae did not appear to have the least effect in reducing their 



numbers ; on the contrary, the total number of all bacteria went up 



The evidence, therefore, strongly points to the fact that larvae in water will 



