32 



ANDREW BALFOUR. 



As regards the action of larvicides in saline waters the experiments of Jacob in the 

 Panama Canal Zone may be cited. Employing the well-known preparation devised 

 for use in that area and consisting of so-called " crude carbolic acid," resin and 

 caustic soda, he proved by laboratory tests that the mineral salts in the salt water 

 do not lessen the toxicity of the larvicide. Moreover, if the larvicide be added as an 

 emulsion (and it is essential that this should be the case, for the sodium salts of the 

 cresols remain insoluble in sea-water), its entire quantity remains on the surface, 

 where it is found deadly to mosquito larvae. Jacob sums up to the effect that 



" When all other conditions are the same, the larvicide applied in an emulsified 

 state is more efficient in brackish water than it is in fresh water, and when 

 brackish water is to be treated, the area of the surface of the water is the 

 only factor necessary to be considered in determining the quantity of 

 larvicide to be used." 



Perry, commenting on this work, stated that his experience in the field confirmed 

 the above results. 



I have not been alile to find records as regards the use of other larvicides in brackish 

 waters, but lack of time has prevented an exhaustive search of the literature, in which, 

 however, I beheve there are but few references to the subject. 



Mosquito larvae have been found in waters containing chemical constituents other 

 than the marine salts, for example, aluminium sulphate, as already mentioned. Some 

 of them, indeed, even survive in solutions which a priori one would imagine should 

 speedily kill them. A consideration of these strange and sometimes sulphurous 

 nurseries would, however, lead us too far afield, but it might well form the subject of 

 another paper containing statements which, though perfectly true, might easily be 

 regarded as incredible. 



References. 



Balfour, A. 



Second Review. Supplement to 

 4th Report, Wellcome Tropical 

 Research Laboratories, Khar- 

 toum, 1911, p. 201. 



Bank-s C. S. 

 Carruthers . . 



Chaoin, C. V 



A mosquito which breeds in salt 

 and fresh water. 



The origin and progress of the 

 malarial fever now prevalent 

 in New England. 



Philippine J I. 

 19(^8, ^'ol. lii 



Sci., Section B^ 

 No. -1, p. 335. 



Presidential Address delivered by 

 Surg.-Gen. C. P Lukis at the 

 second meeting of the Geneial 

 Malaria Committee, Bombay, 

 16th Nov. 1911. (Abstract: 

 Jl. Trop. Mod. & Hyg. 1912, 

 Vol. XV, p. 30.) 



Fisk Fund Prize Dissertation, No. 

 32. Providence, R.I. 1884. 



Chidestf-r, F. E. 



The influence of salinity on the 

 development of certain species 

 of mosquito larvae and its 

 bearing on the problem of the 

 distribution of species. 



New Jersey Agric. Expt. Sta, 

 New Brunswick. Bull. 299. 

 (Rev. in Rev. Appl. Entom. 

 B, 1917, Vol. v., p. 103.) 



Chidester, F. E., & Patter- 

 son, R. 



The influence of various concen- 

 trations of sea-water on the 

 viability of the salt-marsh 

 mosquitoes, A 'ides soUicitans 

 and Aides cantalor (Dip.). 



Entom. News, Philadelphia, vol. 

 xxvii, No. 6. June 1916, p. 272. 

 (Rev. in Rev. Appl. Ent. B, 

 1916, Vol. iv, p. 123.) 



