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 (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 °C to 55 °C at a rate of 0.25 °C min−1. We found that the CTmax of larvae (49.1 °C ± 0.3 °C) was higher than pupae (47.4 °C ± 0.2 °C) and adults (46.9 °C ± 0.2 °C). 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 °C for adults (2.01 ± 0.22) was significantly higher compared to larvae (1.40 ± 0.06) and Q10: 35–45 °C 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.

Heat tolerance variation reveals vulnerability of tropical herbivore–parasitoid interactions to climate change

“…This can potentially cause a cascading effect on host plants and tropical ecosystem functions (Coley, 1998;Marino et al, 2018). It is important to highlight that parasitoids interact with herbivores during caterpillar stage, when herbivore CTmax are generally found to be higher than adults (Bawa et al, 2021;Mutamiswa et al, 2018). This cascading effect might be more serious given the wider heat tolerance mismatch between the trophic levels.…”

Identifying hypotheses for drivers of decline of the bogong moth (Agrotis infusa)

“…It is believed that adult bogong moths cannot withstand the summer hot temperatures typically experienced on the inland plains, unlike other sympatric species such as Helicoverpa armigera (Bawa et al 2021), suggesting that rising temperatures are the trigger that initiates migration from the breeding areas, and additionally drives them upwards to higher elevations after arrival at lower elevations in the mountains. Once in the Australian Alps they congregate in rock crevices and aestivate, save for semi-regular flights during the evening, of unknown purpose.…”