Fig. 1.

Cold acclimation enhances beetle cold hardiness. a Supercooling points (SCPs) of last-instar larval beetles were significantly lower after 4 days of acclimation at 4 °C than those of beetles held at 25 °C (n = 20 for each treatment per day). b Last-instar larval beetles acclimated to 4 °C for 10 days had significantly reduced mortality relative to those held at 25 °C (n = 10 for each treatment). Lethal temperature causing 50% mortality (LT₅₀) was determined by probit regression. The data in a and b are shown as mean ± s.e.m. Two-tailed Student’s t test was used to test significant differences. *P < 0.05; **P < 0.01; ***P < 0.001. AC, low-temperature acclimation (4 °C); Control (25 °C). The last larval beetles used in a and b were collected at 20–22 Oct. 2016 and 20–25 Oct. 2019