We investigated the inquiline communities found in the leaves of the purple pitcher plant Sarracenia purpurea L. No general patterns were found among the abundances of common species or in correlations between biotic and abiotic variables (pitcher volume, sediment volume, pH). Further, no support was found for successional patterns within the pitchers when leaf number was used as an estimate of pitcher age. Experiments were conducted to quantify the effects of two size classes of the mosquito Wyeomyia smithii (Coq.) (Culicidae) and cladocerans (family Daphnidae, subfamily Eurycerinae, species undetermined) on the growth and survival of the small-mosquito size class. In simulated pitchers maintained in growth chambers for 14 days, small mosquitoes and large mosquitoes sup- pressed small-mosquito growth, and large mosquitoes decreased small-mosquito survivor- ship. Cladocerans had no effect on small-mosquito growth or survival. In simultaneous experiments conducted in natural pitchers in the field, large mosquitoes suppressed small- mosquito abundance and growth; no other significant interactions were found.