JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org. This content downloaded from 128.83.ABSTRACT.-Pitcher plants (Sarracenia purpurea L.) attract ovipositing females of pitcherplant midges (Metriocnemus knabi Coq.) and mosquitoes (Wyeomyia smithii (Coq.)) and the pitcher provides an aquatic habitat for the developing larvae. Pitcher age, length, maximum and actual fluid volume of pitchers, hood size and appearance, and amount of organic matter in the pitcher were measured and correlated with abundance of mosquitoes and midges. Midge abundance was positively correlated with the actual amount of fluid in a pitcher, and mosquito abundance was higher in younger larger pitchers with little organic matter. However, pitcher characteristics explained less than half of the variation in larval abundances. Additional factors such as microclimate, interactions within the pitcher community, and stochastic factors may account for the large amount of unexplained variation in larval abundances.