Biting Times of Parous and Nulliparous Simulium damnosum

Abstract

DURING dissections of the biting fly Simulium damnosum in the Sudan in July 1948¹ it was found that the proportion infected with developing Onchocerca worms was nearly twice as high in flies caught before 1 p.m. as in those caught later in the day. Many S. damnosum were dissected at Farangbaia in the Tonkolili valley, Sierra Leone, in October and November 1955, and it was noticed that, on some days at least, more flies with a plentiful fat-body (indicating that they were nulliparous) were present in afternoon than in morning catches. It thus appeared that nulliparous flies tend to bite largely in the afternoon; but no exact figures were obtained because the amount of fat-body is very variable and does not always clearly differentiate parous and nulliparous flies.