Caiusa Surcouf (Diptera: Calliphoridae) is an Old World genus of blow flies, the larvae of which feed on egg masses in the foam nests of various species of rhacophorid tree frogs. Here, we provide the first records for India (West Bengal, Eastern India) of Caiusa coomani Séguy, 1948 and C. karrakerae Rognes, 2015, together with new information on the behaviour and morphology of their larvae. Active surface swimming to disperse from infested nests is documented in blow fly larvae for the first time, as is the presence of a large internal air sac presumably acting as a floating aid. Chiromantis simus (Annandale, 1915) (Anura: Rhacophoridae) egg masses are first recorded as a feeding substrate of Caiusa larvae.
Keywords: Rhacophoridae; Oriental Region; Phumosiinae; West Bengal; blow flies; tree frogs.