HOW DO PREDATOR-INDUCED CHANGES AFFECT PREY VULNERABILITY - LARVAE OFCHAOBORUS-FLAVICANS (DIPTERA, CHAOBORIDAE) FEEDING ON DAPHNIA-PULEX (CRUSTACEA, CLADOCERA)

1. The relative food consumption and prey preferences of fourth-instar larvae of the phantom midge Chaoborus flavicans were investigated in laboratory experiments. Neonates and second instars of two clones of t he cladoceran Daphnia pulex - an Arctic and an European clone - were o ffered to the predatory larvae. Each clone was divided into two groups : one group was exposed to the midge larvae during embryogenesis, wher eas the other was not exposed to the predator. 2. While both exposed a nd unexposed neonates of the European clone had neck teeth, animals of the Arctic clone did not develop these spines. 3. A consistent rank o rder was observed in the vulnerability of the four prey types. Newborn daphnids from the Arctic clone were more vulnerable to predation than those from the European clone. Moreover, differences existed within e ach clone, regardless of neck teeth induction: Daphnia previously expo sed to Chaoborus were less susceptible to the predators than unexposed prey. 4. The results show differences in the vulnerability of exposed and unexposed neonates that are not caused by the presence or absence of neck teeth. Perhaps the reduced vulnerability of exposed neonates was due to predator-avoidance behaviours.