Determination of temperature and relative humidity combinations that are lethal to bed bugs ( <i>Cimex lectularius</i> )

Bed bugs (Cimex lectularius L.) are blood feeders whose survival is significantly influenced by environmental factors such as temperature and relative humidity (RH). Despite their adaptations to survive in harsh environments such as a low net transpiration rate and high critical thermal maximum, their physiological limits to heat and humidity remain underexplored. This study aims to determine the lethal temperature and RH combinations for bed bugs to improve non-chemical pest management strategies. Adult male bed bugs were exposed to 5 temperatures (25, 37, 38, 39, and 40 °C) and 3 RH levels (10%, 45%, and 90%) in controlled incubators for 14 d. Median survival times (MSTs) and hazard ratios were determined using Kaplan-Meier survival analysis. The results revealed that at 37 °C, bed bugs exhibited relatively higher survival (MST > 14 d), particularly at 45% and 90% RH suggesting that physiological mechanisms may mitigate heat stress. However, survival declined to 12 d at 37 °C with 10% RH, and this reduction at low RH was amplified at higher temperatures, where MST fell to 4-6 d at 39 °C and only 3 d at 40 °C. These results demonstrate that dry environments exacerbate thermal stress. At 40 °C, mortality was highest across all RH levels, with the shortest survival time (1 d) observed at 90% RH, which indicates that heat in combination with high humidity is most effective at inducing heat-related mortality in C. lectularius. These findings highlight bed bugs' vulnerability to environmental stressors outside their temperate origins.