Discovery of an underground chamber to protect kings and queens during winter in temperate termites

Abstract

Overwintering is a critical part of the annual cycle for species that live in temperate, polar, and alpine regions. Consequently, low-temperature biology is a key determinant of temperate species distribution. Termites are distributed predominantly in tropical regions, and a limited number of species are found in the temperate zone. Here, in the termite Reticulitermes speratus, we report the discovery of an underground chamber that protects kings and queens to survive the winter, which is separate from the one they used during the warmer breeding season. In the spring, the royals inhabited decayed logs on the ground, then moved to their underground chamber located in the roots of stumps in the fall. The winter minimum temperature measured in the royal chamber was higher than that in the logs on the ground. In overwintering termites, the kings and queens had higher cold tolerance than workers and soldiers. Air temperatures dropped below the critical temperature multiple times, as evidenced from the past 140 years of weather records in Kyoto. These results demonstrated the survival strategies of reproductives to overcome the environment at the latitudinal limits. This study helps further the understanding of the termite’s seasonal phenology, long-term survivorship, and life cycle.

Estimation of the Damage Risk Range and Activity Period of Termites (Reticulitermes speratus) in Korean Wooden Architectural Heritage Building Sites

“…At the individual level, termites have the ability to alter the composition of their carbohydrate metabolites as well as balance their body water content and total lipids as a physiological strategy to adapt to the cold [41]. In addition, an evaluation of termite survival in response to temperature changes revealed a substantial decrease in their survival during short-term cold exposure when temperatures were lower than −8 • C for kings and queens and lower than −4 • C for soldiers and worker ants [42]. Even when subject to low temperatures, termites require a specific duration to die.…”

“…However, during the winter months, they moved to the underground royal chamber, where the temperature remained consistently high compared to the outside environment. The royal chamber, where the king and queen wintered, was located 15 to 37 cm below ground, and the inside temperature remained stable at 5 to 10 • C during January and February [42]. Due to their social nature, termites are not readily exposed to low temperatures that might lead to freezing.…”