A comparison of three methods for collecting dipteran insect larvae which inhabit the northern pitcher plant (Sarracenia purpurea)

Three methods for collection of dipteran insect larvae from the leaves of the northern pitcher plant Sarracenia purpurea were examined. The "turkey baster" method (Addicott, 1974) proved inadequate for quantitative samples of the larval insects. A modified version of a suction apparatus (Fish and Hall, 1978) produced samples with errors. Samples obtained with a suction apparatus yielded higher proportions of the culicid population than of the chironomid population. This was due to the difference in location within the pitcher of each species; the chironomids tend to be in the organic matter in the pitcher, while the culicids are generally free-swimming. The only method that consistently yielded reliable quantitative samples of all insects living in the leaves was the removal method, in which whole leaves were taken from the plant and dissected in the laboratory. However, when destructive sampling is precluded, samples obtained with a suction apparatus may yield acceptable results for culicids.