The results of the present investigation are based on the adaptation of liverfluke cercariae in immature stages of Anopheles fluviatilis at altering temperature, light conditions and pH of the water. The prevalence of cercariae was maximum in IV instar larval stage at 24°C and 40°C whereas in III instar larvae it was 32°C. The pupae also exhibited antagonism efficiency but to a less extent in comparison to II, III and IV instar larvae. There was no response to I instar larvae towards the cercariae at all the selected ecological parameters. The adaptation efficiency of cercariae was maximum in III instar larvae and that too in sharp light conditions whereas in dim light and darkness it was observed in IV instar larvae. At both the levels of pH i.e. 6.5 and 7.5 the maximum prevalence of adaptation was seen in IV instar stages followed by III instar larvae