"On some of the Central African lakes in the dry season a minute midge, one of the Chironomidae, rises from the water in clouds so dense that from a distance the effect is that of smoke. Near Lake Nyasa the midges are known as kungu and round out the larder of many of the shore tribes. When great hosts of them are driven landward by the wind, they are swept off the bushes and rocks by the natives or caught against mats hung up for the purpose; they are then compressed into oily cakes, roasted, and eaten. According to Koch, the Sesse Islanders collect and prepare in a similar manner the may flies which swarm in dense columns over Lake Victoria."
Reference: Natural History Magazine