Effects of Feeding History on Short-Term and Long-Term Functional Responses in Notonecta hoffmanni

Abstract

SUMMARY (1) Growth rate and size at moult increased with prey density for Notonecta hoffmanni Hungerford nymphs raised at various densities of their mosquito larvae prey. (2) The functional response of different sized instar IV nymphs was type-2, and large predators ate more at high prey densities than did small predators. (3) The feeding rate of individual predators did not vary in any regular way during the instar. Predator size at the start of the instar was a good predictor of the predators' functional responses for both long- and short-term experiments. Short-term experiments were good predictors of the long-term functional responses: the relationship between these two responses remains linear over a wide range of prey densities. These facts allow us to predict the functional response over the whole instar from a knowledge of predator weight. (4) Variation in predator size within one instar (IV) was as important as differences in the predators' size in different instars in determining the predator's feeding rate.