USE OF MORPHOLOGICAL CHARACTERS IN STUDY OF SIMULIUM-DAMNOSUM SL POPULATIONS IN WEST-AFRICA

Abstract

Morphological characters were tested which could be used to compare and to associate S. damnosum populations reinvading the area of the Onchocerciasis Control Program in the Volta River Basin [West Africa] with those of potential source areas. The savanna cytospecies S. damnosum and S. sirbanum were distinguished from the forest species S. sanctipauli, S. soubrense and S. yahense by the size and shape of the antennae and the color of the basal wing tufts. Wing tufts of S. squamosum were of variable color. Results did not confirm morphological keys for the complex which used counts of maxillary teeth to separate S. damnosum and S. sirbanum, and numbers of spinules on the radial vein of the wings to separate S. yahense and S. squamosum. Populations of the S. damnosum complex were characterized by morphometric methods. Measurements of the length of the thorax provided a rapid and easy means to distinguish different populations. The length of the thorax was positively correlated with the length of the wings. By using several measurements in combination populations could be more clearly characterized.