Enhancing hive microclimate of Apis cerana colonies using passive thermal insulation techniques

Abstract

Apis cerana, the native honeybee species of Sri Lanka, plays a pivotal role as a primary pollinator in both agriculture and biodiversity. However, environmental stress, particularly fluctuations in temperature (T) and relative humidity (RH), can negatively affect colony health and hive stability, increasing the risk of colony migration. Passive thermal insulation offeresa potential low-cost, eco-friendly solution, yet it remains understudied in Apis cerana management. This study evaluated the influence of internal and external temperature and RH on Apis cerana colonies and assessed the effectiveness of passive insulation. Ten healthy colonies of similar strength were housed in eight-frame hives and randomly assigned to treatments. Colonies were maintained under identical conditions within the same apiary. Two natural insulating materials, wood shavings and clay brick particles, were applied around hive walls and beneath the roof. Temperature and RH were recorded using digital sensors (DHT22) placed centrally inside the hives. Colonies were inspected one day intervals, and photographic monitoring was conducted biweekly to assess the brood area, bee coverage and comb construction. Optimal internal T and RH conditions for colony stability were identified as 33–36 °C and 60–70%, respectively. Statistical analysis was performed using one-way ANOVA to compare internal and external environmental conditions. Hives with wood shavings maintained an average internal temperature of 33.51 ± 0.11 °C and RH of 76.66 ± 2.03%, with significant differences from external conditions (temperature p = 0.00397; RH p = 3.37 × 10⁻¹⁰). Hives with brick insulation recorded an average temperature of 34.43 ± 0.12 °C and RH of 75.73 ± 0.24%, also showing significant differences (temperature p = 0.00048; RH p = 0.00034). These findings confirm that passive insulation effectively regulates hive microclimate and reduces environmental stress, supporting its application in sustainable, low-cost beekeeping, particularly for rural communities, while contributing to the growth of Sri Lanka’s apiculture sector.