Communal Oviposition in Simulium damnosum Theobald (Diptera, Simuliidae)

Abstract

Simulium damnosum is the main vector of human onchocerciasis over a large part of tropical Africa. Although a considerable amount of work has been done on the habits of this insect—as summarized by Freeman and de Meillon¹—there are many points in its biology which are still obscure, one of the most important of these being the normal method and site of oviposition. The only published description of the egg-laying habits of this species is that of Wanson and Henrard², who recorded thirty-five egg batches on specially attractive breeding sites mainly in the form of floating and vertical artificial frameworks of Pennisetum stems. Eighteen of these batches were deposited on the floating stems, thirteen on the vertical stems and four on artificial accumulations of stones. Ovipositing females did not penetrate the water but were observed to lay their eggs at or just above water-level; the egg batches consisted of 200–250 eggs. There is no record of the time of day on which oviposition was observed.