Notwithstanding the work which has been conducted during the last few years on blood-sucking flies, and particularly on those which occur in Tropical Africa, owing to their connection, whether proved or merely suspected, with the spread of various diseases of man and animals, nothing has hitherto been published on the life-history of any African species of the large family Tabanidæ, except in the case of Tabanus biguttatus, Wied.* It is hoped, therefore, that the following notes on the bionomics of two of the more common Tabanids, though incomplete, may nevertheless be of some interest.