Estimating the differences in critical thermal maximum and metabolic rate of Helicoverpa punctigera (Wallengren) (Lepidoptera: Noctuidae) across life stages

Temperature is a crucial driver of insect activity and physiological processes throughout their life-history, and heat stress may impact life stages (larvae, pupae and adult) in different ways. Using thermolimit respirometry, we assessed the critical thermal maxima (CT_max-temperature at which an organism loses neuromuscular control), CO₂ emission rate (V́CO₂) and Q10 (a measure of V́CO₂ temperature sensitivity) of three different life stages of Helicoverpa punctigera (Wallengren) by increasing their temperature exposure from 25 ^oC to 55 ^oC at a rate of 0.25 ^oC min^-1 . We found that the CT_max of larvae (49.1 ^oC ± 0.3 ^oC) was higher than pupae (47.4 ^oC ± 0.2 ^oC) and adults (46.9 ^oC ± 0.2 ^oC). The mean mass-specific CO₂ emission rate (ml V́CO₂ h^-1) of larvae (0.26 ± 0.03 ml V́CO₂ h^-1) was also higher than adults (0.24 ± 0.04 ml V́CO₂ h^-1) and pupae (0.06 ± 0.02 ml V́CO₂ h^-1). The Q₁₀: 25-35 ^oC for adults (2.01 ± 0.22) was significantly higher compared to larvae (1.40 ± 0.06) and Q₁₀: 35-45 ^oC for adults (3.42 ± 0.24) was significantly higher compared to larvae (1.95 ± 0.08) and pupae (1.42 ± 0.98) respectively. We have established the upper thermal tolerance of H. punctigera, which will lead to a better understanding of the thermal physiology of this species both in its native range, and as a pest species in agricultural systems.