An examination of insect capture capacities and inquiline larvae communities in Sarracenia purpurea with respect to pitcher hood morphological adaptations.

Abstract

The purple pitcher plant (Sarracenia purpurea) requires both capture of prey insects to supplement nutrients from the nutrient‐poor soil in which they live and inhabitation by Diptera larvae to digest these nutrients. We wish to determine if hood morphology in the purple pitcher plant has evolved to attract prey or to suit female mosquito (Wyeomyia smithii) and midge (Metriocnemus knabi) preferences for oviposition sites. We measured various aspects of hood morphology (height, width, opening width, surface area and opening area), and rated each pitcher on a scale of percent red coloration, and related each of these factors to number of captured prey, number of larvae, and biomass of all dry contents of the pitcher.All components of pitcher hood size and opening were found to have a significantly positive relationship with inquiline larval populations, and greener pitchers had both a significantly higher proportion of larval populations and populations of significantly greater size than red pitchers. In contrast, the number of prey captured was not related to either pitcher morphology or color. We conclude that increased pitcher hood size and opening size, as well as greener pitcher color, are preferred by mosquito and midge females for oviposition sites, but these attributes do not increase prey capture success.