2 DECEMBER 1911, Page 34


[To THE EDITOR Or THE " SPECTATOR."] SIR,—Some of your readers will probably be glad to know that Dr. W. B. Graham, Director of the Medical. Research Institute at Lagos, has discovered a small fish that preys on mosquito larva: in Southern Nigeria. The mode of his dis- covery resembles so closely facts related in your article on the Barbados millions in the Spectator of August 19thlast that it seems worth while to have the matter recorded. Dr. -Graham noticed that certain swamps which presented ideal breeding places for mosquitoes were absolutely free from mosquito larva?. The only fish inhabiting the swamps were those of the species, apparently a new one, of the Cyprino- donticla, which has been named by Mr. Boulenger Haplochilus Grahami. This fish could easily be utilized for mosquito- destroying purposes in cisterns and in pools free from other fishes which might prey upon it. It is doubtful, however, whether the Haplochilus will prove as useful as the Barbados millions, as it seems to confine its voracious instincts to the larva) of the mosquito, rejecting the pupm and careless of the mature mosquito when laying her eggs on the water. Much the same has- to be said regarding two- other West African relatives of the millions noticed by Mr. Gowdey, Government Entomologist in -Uganda, which refuse to live in swamps which are overgrown with reeds and grasses where the mosquito swarms and multiplies in unchecked prodigality.—