The life-cycle of Pleurogenoides ovatus Rao, 1977, infecting the frogs, Rana tigrina and R. cyanophlyctis has been elucidated. All the life-cycle stages from egg to egg-producing adults were successfully established in the laboratory. The life-cycle took about 80 days for completion. Cercariae were found in the freshwater snail, Digoniostoma pulchella, collected from paddy fields at Chelembra, Malappuram district of Kerala, during the monsoon months. Cercariae are of the virgulate xiphidiocercous type. Metacercariae occurred in the connective tissues, hepatopancreas and musculature of the freshwater crab, Paratelphusa hydrodromous. The growth and development of the metacercariae in P. hydrodromous have been studied in detail. Frogs became infected when they fed on infected crabs. The prepatent period is 10 days.

The life-cycle stages of Pleurogenoides malampuzhensis sp. nov. infecting the Indian bullfrog Hoplobatrachus tigerinus (Daudin) and the skipper frog Euphlyctis cyanophlyctis (Schneider) occurring in irrigation canals and paddy fields in Malampuzha, which forms part of the district of Palakkad, Kerala, are described. The species is described, its systematic position discussed and compared with the related species, P. gastroporus (Luhe, 1901) and P. orientalis (Srivastava, 1934). The life-cycle stages, from cercaria to egg-producing adult, were successfully established in the laboratory. Virgulate xiphidiocercariae emerged from the snail Digoniostoma pulchella (Benson). Metacercariae are found in muscle tissues of dragonfly nymphs and become infective to the frogs within 22 days. The pre-patent period is 20 days. Growth and development of both metacercariae and adults are described.

The life-cycle of Tremiorchis ranarum Mehra and Negi, 1926 (Trematoda: Plagiorchiidae) infecting Rana tigrina and R. cyanophlyctis is elucidated. Life-cycle stages, from egg to egg-producing adults, were successfully established in the laboratory. Life-cycle took more than two months for completion. Cercariae were found in the snail, Pila virens collected from paddy fields at Chelembra in the Malappuram district of Kerala during the monsoon months. Cercariae are of the xiphidiocercous type. Metacercariae occurred beneath the skin and in head, tail and body musculature of tadpoles of R. tigrina and R. cyanophlyctis. Adult frogs are refractory to cercarial infection. Frogs became infected when they fed on tadpoles containing metacercariae. Successive stages in the development to adult from the metacercariae were followed. Chronological synchronization in the reproductive activity of the host and the parasite is briefly discussed.

Two new species of Myxobolus, Myxobolus puntiusi sp. nov. from the heart wall, and Myxobolus ticto sp. nov. from the gills, muscles, intestine and liver of the two-spotted barb, Puntius ticto punctatus Day are described.

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