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

Abstract

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 (CTmax-temperature at which an organism loses neuromuscular control), CO2 emission rate (VCO2) and Q10 (a measure of VCO2 temperature sensitivity) of three different life stages of Helicoverpa punctigera (Wallengren) by increasing their temperature exposure from 25 ℃ to 55 ℃ at a rate of 0.25 ℃ min−1 We found that the CTmax of larvae (49.1 ℃ ± 0.3 ℃) was higher than pupae (47.4 ℃ ± 0.2 ℃) and adults (46.9 ℃ ± 0.2 ℃). The mean mass-specific CO2 emission rate (ml VCO2 h−1) of larvae (0.26 ± 0.03 ml VCO2 h−1) was also higher than adults (0.24 ± 0.04 ml VCO2 h−1) and pupae (0.06 ± 0.02 ml VCO2 h−1). The Q10: 25–35 ℃ for adults (2.01 ± 0.22) was significantly higher compared to larvae (1.40 ± 0.06) and Q10: 35–45 ℃ 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.