Thesis (M.Sc.) - Cairo University - Faculty of Science - Department of Entomology

The freshwater snails, Lymnaea natalensis, Bulinus truncatus and Biomphalaria alexandrina are intermediate hosts of Fasciola gigantica, Schistosoma mansoni and Schistosoma haematobium which are economically and medically important parasites. The Odonata, Hemianax ephippiger nymph and the Hemiptera, Sphaerodema urinator adult share the same habitat of snails in ponds, lakes and streams. To evaluate the predatory capacity of those predators as bio-control agents for the freshwater snails, observations on the searching, attacking and devouring of the snails with a series of laboratory-based predation experiments, which aimed at determining daily predation rate, differential predation on small-, medium- and large-sized snails. This study also evaluated the preference of the Odonata nymph and the water bug adult towards the three snail types. Laboratory evaluation revealed that, the Odonata nymph and the water bug could kill and consume all the three sizes of the three snail types where searching and handling times of the predators differed depending on the snail size and the predator vulnerability. The predation rate varied also with respect to snail size and density where the snail type and size were the major factors influencing the predator preference. This study suggested that the predators, H. ephippiger nymph and S. urinator adult may be suitable bio-control agents of L. natalensis, B. truncatus and B. alexandrina snails population

Issued also as CD