Experimental methods
Ten glass aquaria, 5 L in total volume, containing 3 L of
pond water were used in each experiment. Among these, the
experimental group was comprised of five glass aquaria, each
containing a predator and experimental snails. The remaining
five glass aquaria constituted the control with only snails. The
aquaria were covered with nylon net to prevent snail escape.
Snails that may leave the water and sit on the aquarium wall
were not considered and deleted from the count. The snails were
allowed to acclimatize for 1 h before introducing the predator.
Snails and Odonata nymphs were used only once in the experiments.
All experiments were carried out at constant temperature
of (25 ± 2) C, 60%–70% relative humidity. Fluorescent tubes
(10 cm long, 32 watt, were placed 100 cm above the tanks to
provide a photo period of L12: D12.