In dealing with this extremely interesting and valuable collection of Mosquito larvæ and pupae from Lagos, which we owe to the industry of that indefatigable collector and observer, Dr. W. M. Graham, I have endeavoured to give a practical and not too technical description of each species, and I have given illustrations of all tbe principal characters, and of some points of more general interest. If technicalities are indulged in, they are explained in the preliminary text, and in the plates. It has been my object to make it impossible for the careful worker to mistake any one of these larvæ for that of another species, but persons who have experience of such work, know the difficulty of arriving at such results without a knowledge of all known forms, and that knowledge I have no pretensions to possess.