Fig. 4. Typical recording of a hyperoxic switch recording of Pogonomyrmex californicus. One ant, mass 8.25 mg, at 40°C and 20 ml min^–1 STP. The recording begins and ends with baselines. The large dip in _CO2 that follows hyperoxia is plainly visible. The drop in _H2O coincides with the drop in _CO2. Following the introduction of nitrogen, a rapid rise in both _H2O and _CO2 are evident. _CO2 rapidly declines to near baseline levels, but _H2O plateaus at an intermediate level; see text.