A few years ago, when I discussed the black-flies observed during the first Harvard African Expedition (1926–27), I could find definite records of only two species from the Belgian Congo, and a brief reference to a third, unnamed species. Simulium neavei Roubaud was subsequently added to the Congo list by Dr. J. Hissette. Since the number of species known from tropical Africa has been increasing steadily, now reaching fifty-seven, it was to be expected that several more species would be discovered in the Belgian Congo.
The second Harvard African Expedition of 1934, organized for the special study of onchocerciasis, observed adults of four species, while ten others were bred from pupae. In the course of our observations on the ecology of these flies, we were greatly assisted by Dr. J. Hissette. At my suggestion, Dr. Hissette continued the investigation of the Simuliidae after the Harvard Expedition's departure.