Fig. 7. Critical oxygen partial pressure (P_c) values for mass-specific CO₂ emission (_CO2) determined in multiple ways and for abdominal pumping versus instar. Each symbol indicates the median; error bars mark the 25th and 75th percentiles. (A) P_c for _CO2 determined using 95% confidence intervals (N=8 for each treatment group), (B) P_c for abdominal pumping (N=8 for each group), (C–E) P_c determined as the oxygen partial pressure (P_O2) when _CO2 decreases below 75%, 50% or 25% of normoxic _CO2 (N=8 for each group) and (F) P_c determined using paired t-tests to identify the first P_O2 at which mean _CO2 from Fig. 6 was significantly lower than normoxic _CO2.