The fecundity ofSimulium damnosum s.l.in northern Togo and infections withOnchocercaspp.

The numbers of maturing oocytes in gravid Simulium damnosum s.l. were related to the sizes of the flies and when this was taken into account the numbers fell into two groups. It was concluded that the group with the highest oocyte counts were nulliparous and that the remainder were parous flies. No evidence was found to suggest that flies in their third or subsequent gonotrophic cycles matured fewer oocytes than those in their second cycles. However, the results did suggest reduced fecundity of those flies infected with Onchocerca spp. The frequency distributions of the Onchocerca spp. infections for each of three different stages can be fitted to negative binomial distributions with similar values (0·04–0·07) for the parameter k.