Cold tolerance and prediction of northern distribution of Histia rhodope (Lepidoptera: Zygaenidae) in China

Histia rhodope (Cramer) (Lepidoptera: Zygaenidae) is one of the most destructive defoliating pests of the landscape tree Bischofia polycarpa (Levl.) S in China and other Southeast Asian regions, posing a critical threat to urban landscapes and their ecological benefits. This pest has shown a trend of northward range shift in recent years in China, making it urgent to understand its potential distribution. This study investigated the cold tolerance of overwintering H. rhodope larvae from October 2022 to March 2023 and estimated their overwintering potential in China. The results showed that the supercooling points (SCP) differed significantly across months. The SCP tended to decrease as the ambient temperature dropped until January, after which it gradually increased until the end of winter. The highest monthly mean SCP was -7.5 ± 2.22°C (October 2022), while the lowest monthly mean SCP was -15.09 ± 2.61°C (January 2023). The mortality rate increased with longer exposure times and lower exposure temperatures but decreased as winter progressed. Moreover, 50% and 90% lethal temperature (Ltemp50 and Ltemp90) exhibited a similar trend, decreasing to a minimum in January 2023, which indicates increased cold tolerance during the colder months. Using Ltemp90 in January as the isotherm for its northern limit indicated that H. rhodope may be limited by low temperatures along the 40°N latitude. These results provide a basis for predicting the dispersal potential and possible geographic range of this pest in China.