Fig. 7. Effect of x-ray beam on CO₂ release in Pterostichus stygicus. Traces from two specimens are shown, depicting extremes of the response to irradiation. The beetle (mass 219.5 mg) in A shows no change in average CO₂ pulse frequency (15.7 min^–1) or volume (0.013 µl), whereas the beetle (mass 166.3 mg) in B shows an increase in both frequency (8.1 to 16.2 min^–1) and volume (0.004 to 0.024 µl).