Fig. 1. Schematic diagram of the apparatus (not drawn to scale). (A) The chamber used for repetitive stimulation of the cockroaches. Stimuli consisted of 2 s rotation (1 cm motion) of the chamber and simultaneous pulse of CO₂ (peak concentration <1%). One chamber was scheduled to present stimuli continuously at the rate of 1 min^–1 (SD group) and another chamber ran with a schedule of 6 h cycles with 3 h of stimuli at 2 min^–1 and 3 h without stimuli (SC group). The study started with 15 animals per chamber. (B) Closed respirometry was used to measure oxygen consumption of individual cockroaches. Respiratory CO₂ was absorbed by Ascarite^TM, and the change in chamber gas volume due to consumption of O₂ was recorded every 10–20 min by measuring the position of a fluid indicator in the side arm. Ten animal chambers and four thermobarometers were all submerged to the level of the side arm in a constant-temperature water bath and studied simultaneously.