Capture rates of invertebrate prey by the pitcher plant, Sarracenia purpurea L.

I examined capture rates of invertebrate prey by pitchers of the purple pitcher plant Sarracenia purpurea,in western Newfoundland, Canada. While captures were diverse, Hymenoptera (mostly ants), Coleoptera and Gastropoda accounted for 69% of the total dry mass caught. Gastropoda decompose quickly and completely in pitchers, and their importance (20%) implies that prey sampling methods that do not survey freshly caught prey may seriously underestimate resource availability in pitchers. The average pitcher caught 11 mg dry mass of animal biomass over its lifetime, but capture rates were highly variable (range 0-67 mg). Pitchers opening earlier in the season caught no more or less than those opening late. Larger pitchers caught more than smaller ones, although size accounted for a small fraction of total variance. Capture rates changed with time, peaking in pitchers 12-33 days old; however, pitchers continued to catch prey through their 2nd season (i.e., after overwintering). In an average pitcher, 2nd-season captures made up nearly half of the total.