Abstract

Field investigations were made in 1991 and 1992 in Kwangju and the western and central Chonnam area to determine the distribution of Lymnaea viridis, the intermediate host of Fasciola hepatica, and to study their life history during the different seasons. It had a wide distribution, existing all over the places, and the principal habitats of the snail were rice paddies. The life cycle was determined by making frequent visits to a series of habitats. The snsils began to produce egg masses in April, and egg production was the highest in May and June. Egg laying was continued but decreased in summer. There was sudden decrease in egg production in October when the temperature was below 2$0^{\circ}C$. The number of snails in July. Under the unfavourble conditions the snail either crawle up on the snail to aestivation. At low temperature below 8$^{\circ}C$ the snails hibernated inthe mud of the habitat. It was found in some habitats thao the snails were loving together with L. auricularia and Physa s pp. which indicates the neccessity of differentiation among them.