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Abstract:
Sixty Chaoborus flavicans 4th instar larvae were enclosed individually in a 1 m deep laboratory system, designed to mimic the thermal and light conditions of a stratified lake, and their vertical displacements were monitored for over 30 days. Though separated, the larvae exhibited a synchronous behavior either when exposed to a chemical stimulus from fish, or when left undisturbed without any predator cues. Under low predator stress the animals moved asynchronously and an averaged population depth displacements poorly reflected the behaviour of individual larvae. These observations support the concept of diel vertical migration as an evolutionary stable strategy.
