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Effect of modified atmospheres (MAs) containing CO2 at 20, 40, 60 and 80% or containing N2 at 97 and 98% on the mortality of Corcyra cephalonica Stainton (Lepidoptera: Pyralidae) sixth instar larvae was studied to determine the LT values at 30 °C. The respiration rates of untreated and treated larvae with 60% CO2 and/or 98% N2 at LT50 were measured using Q-Box RP1LP low range respirometry package. Total protein and triglycerides of treated and untreated larvae were assayed. Complete larval mortality was recorded after 72 and 144 h of treatment with 60% CO2 and 98% N2, respectively. Calculated LT50 values were 39.3 at 60% CO2 and 87.5 h at 98% N2 MAs. Respiration quotient (RQ) in the light of consumed O2 and produced CO2 of untreated larvae was 1.0 while it was 0.85 at 60% CO2 and 0.72 at 98% N2. Duration time necessary for produced CO2 curve to reach the maximum point (2000 ppm) was significantly shorter at untreated larvae (27.64 min) in comparison with that recorded at CO2 (35.48 min) which also significantly less than that obtained at N2 (98.54 min). At all treatments, total protein was decreased while triglycerides were increased in comparison with control. [ABSTRACT FROM AUTHOR]