Population density, size frequency, and reproduction of the pulmonate gastropod Physella cubensis living in a central Alabama stream and ephemeral pond habitat were assessed over a three-year period from January 1989 through December 1991. These parameters covaried seasonally and from year to year with fluctuating environmental temperature and precipitation. Population dynamics of ephemeral pond snails were also affected by episodic drying events. Physella cubensis is able to survive habitat desiccation in ephemeral pond habitats by burrowing into the hypopheric zone of the sediments. This behavior is displayed only by juvenile snails (1-5 mm shell length). Overwintering in the sediments is restricted to young adult snails (5-8 mm shell length). Food quality and particularly temperature were found to influence growth and survivorship. Optimum temperature for growth and survivorship was 25°C (vs. 15°C and 35°C). Snails raised at 15°C and 25°C exhibited a dramatic shift in the timing of first oviposition (60 vs. 18 days, respectively), but did not differ significantly in body size at first reproduction. Snails raised at 35°C appeared thermally stressed and failed to oviposit. Food quality influenced reproductive output, with only snails fed medium- and high-quality diets producing eggs. Both field and laboratory studies indicate that P. cubensis living in a warm-temperate climate ex-emplify an opportunistic life history strategy in which such traits as rapid juvenile growth and attainment of maturity, shortened lifespan, high fecundity, and constant reproduction over the duration of the adult lifespan are favored.