Predation of beetles (Tenebrio molitor) infected with tapeworms (Hymenolepis diminuta): a note of caution for the Manipulation Hypothesis

Previous laboratory studies have indicated that tenebrionid beetles infecte d with Hymenolepis diminuta display behavioural alterations. These are assu med to increase the likelihood of this intermediate host being predated by the Rattus sp. definitive host, and hence provide support for the Manipulat ion Hypothesis. We tested this hypothesis by both assessing beetle behaviou r and predation rates in semi-naturalistic environments. Behavioural assays showed that infected beetles were more often exposed (not concealed under boxes) than uninfected beetles. However, there were no differences in preda tion rates between infected and uninfected beetles. We discuss this in term s of the historical and evolutionary contexts under which such altered beha viours could evolve and their implications for the Manipulation Hypothesis.