Effects of soil moisture on tunneling, survivorship, and food consumption of the Formosan and eastern subterranean termites (Blattodea: Rhinotermitidae)

Abstract

Soil moisture is a critical environmental factor for the survival and behavior of subterranean termites (family Rhinotermitidae). The invasive Formosan subterranean termite, Coptotermes formosanus Shiraki, and the native eastern subterranean termite, Reticulitermes flavipes (Kollar), co-occur in the southeastern United States, while R. flavipes is distributed in a wider geoclimatic range. Previous studies showed that subterranean termites preferred higher soil moisture levels for tunneling and feeding; however, the impacts of constant moisture remained to be characterized to understand their moisture tolerance. In this study, we hypothesized that different soil moisture regimes can alter termite foraging and survival, and that the effects differ between the two species. The tunneling activity, survivorship, and food consumption of termites were documented for 28 days with different sand moisture conditions ranging from no moisture to full saturation (0%, 1%, 5%, 15%, 25%, and 30%). We found that there were no significant differences in the responses between C. formosanus and R. flavipes. In both species, termites did not survive or tunnel with 0% moisture. Termites performed tunneling with only 1% sand moisture, although they did not survive for 28 days. A minimal of 5% sand moisture was required for survival, and there were no significant differences in survivorship, tunneling activity, or food consumption among moisture contents of 5-30%. The results suggest that subterranean termites are resilient to moisture extremes. Colonies can tolerate low moisture conditions in their foraging environment for extended times, which may allow them to tunnel and find new moisture sources for colony survival.

Keywords: Coptotermes formosanus; Reticulitermes flavipes; climate adaptation; invasive species; water availability.