Observations on sampling pre-imaginal populations of blackflies (Dipt., Simu liidae) in West Cameroon

Abstract

The use of standardised artificial substratum units (SASUs) for sampling preimaginal populations of Simulium is reviewed and the results then given of experiments with SASUs in rivers and artificial streams in West Cameroon in 1968–70. The increase of downstream drift of larvae by night is attributed to the increased activity of associated fauna at night. The numbers of larvae settling on SASUs is partly afunction of how long the latter have been set and partly due to the pattern of fluctuation in river depth. Any particular SASU appears to be selective in relation to the different species of Simulium available for settlement. A new index of uniformity is proposed for comparing the diversity of Simulium faunas occurring on different substrata.