The larvae were reared in different sublethal concentrations of tannery and paper and pulp mill effluents for 3 weeks. The tannery effluent was found to shorten the time taken for the first moult in captivity, whereas the paper and pulp mill effluent arrested moulting in the larvae. It is inferred that the effluents from the tannery and the paper and pulp mill could have a juvenomimctic (mimic of juvenile hormone) effect on the dragonfly larvae, inhibiting moulting and growth.