Effect of Salt Concentration and Reaction on the Development of Anopheles Larvae

Abstract

Experiments are reported on the effect of salinity on Anopheles larvae. It is shown that A. elutus, A. superpictus and A. sergenti show a decided selective capacity for egg-laying, depositing more than 75 per cent, of their layings in fresh water or water of low saline content. It is also shown that salt concentrations of M/4 and higher are toxic to these eggs and larvae. In so far as reaction is concerned a slightly acid reaction (pH 6·6 to 6·8) favours more active development, although larvae will develop in alkaline solutions. The reaction of the medium also seems to modify the effect of the salinity. In an alkaline substrate M/8 salt solution is more favourable than lower salt concentrations, whereas in acid substrates the reverse seems to be the case.