Susceptibility of schistosome host snails to predation by sciomyzid flies (Diptera: Sciomyzidae) in South Africa

Afrotropical sciomyzids are predators of freshwater pulmonate snails. Studies have indicated that these flies may play a role in controlling medically important (target) snail populations, especially snail intermediate hosts of schistosomes. This study investigated the preferential feeding of Sepedon scapularis and S. neavei on four commonly-occurring molluscs in South Africa. The feeding behaviour of these flies was observed on a polyphagous diet consisting of Bulinus tropicus, Bu. forskalii, Bu. africanus and Biomphalaria pfeifferi. Laboratory experiments were set up with a constant number of 12 live snails per petri dish. Snail mortality was recorded daily for the duration of the larval period. Preliminary results show that both fly species fed preferentially upon Bu. africanus and Bi. pfeifferi. Overall, S. neavei killed more target snails than S. scapularis did. The preference of both fly species was Bi. pfeifferi, followed by Bu. africanus, Bu. tropicus and Bu. forskalii. These sciomyzid species are, therefore, potential candidates as biological control agents of medically-important snails. Whilst these findings are based on laboratory studies, they need to be validated by field trials.