[Mermithids as biological control agents of blackflies]

About 80 species of mermithids parasitic in blackflies have been recorded from the Ethiopian and Holarctic regions. Species of three genera, Mesomermis, Gastromermis and Isomermis, are most common parasites of blackflies. Critical periods during the ontogenesis of all mermithids are associated with the penetration of infective larvae into the host and protective reactions of the later. Intraspecific hybridization of the parasites is recommended in order to increase the effectiveness of mermithids as agents of biological control of blackflies.