The effects of thermal acclimation on lethal temperatures and critical thermal limits in the green vegetable bug, 'Nezara viridula' (L.) (Hemiptera: Pentatomidae)

According to geographical distribution, 'Nezara viridula' (Heteroptera: Pentatomidae) can be found across tropical, subtropical, and temperate regions and this pattern is assumed to reflect differences in thermal adaptation, particularly in cold tolerance. Here the lethal temperature (LT) and critical thermal limits (CTL) (thermal tolerance) are examined for 'N. viridula'. The upper LT for 'N. viridula' at two contrasting climate locations (Breeza and Grafton, New South Wales, Australia) was 40.3°C with 20% survival under the stress of high temperature. The lower LT did not differ between these two populations and was -8.0°C with 20% survival under low temperature stress. Survival of 'N. viridula' increased after acclimation at high temperature for 7 days. In contrast, when acclimated at lower temperatures (10 and 15°C), survival of Breeza and Grafton 'N. viridula' was lower than 20% at -8.0°C. Control-reared 'N. viridula' adults (25°C) had a mean CTMinOnset (cold stupor) of 1.3 ± 2.1°C and a mean CTMax (heat coma) of 45.9 ± 0.9°C. After 7 days of acclimation at 10, 20, 30, or 35°C, 'N. viridula' adults exhibited a 1°C change in CTMax and a ~1.5°C change in CTMinOnset. CTMax and CTMinOnset of Breeza and Grafton 'N. viridula' populations did not differ across acclimation temperatures. These results suggest that short-term temperature acclimation is more important than provenance for determining LTs and CTL in 'N. viridula'.