Morphological identification of simulium sanctipauli and S. yahense in Liberia and comparison of results with those of enzyme electrophoresis.

Simulium sanctipauli and S. yahense have been incriminated as the main vectors of Onchocerca volvulus in the rain-forest zone of Liberia. An accurate identification of the females of the two species which breed in different types of water-courses but are morphologically similar is essential for a proper study of their epidemiological importance and the planning of control measures. Various external characters were examined for their diagnostic value by the comparison of identifications using these characters and those based on enzyme electrophoresis (phosphoglucomutase, trehalase). It was shown that the females of the two species can be separated reliably by the use of external morphological characters. The occasional finding in the same fly of phosphoglucomutase variants typical for each species indicated the possible occurrence of natural hybridization between S. sanctipauli and S. yahense.