The structure and importance of nest mounds in a tropical ant Diacamma indicum

Abstract

1. Nest mounds are an integral part of many subterranean insect species, and they aid in thermoregulation, gaseous exchange, and flood prevention. Ants living in subterranean nests are prone to nest flooding particularly during monsoons and this will impact the colonies' fitness.2. Diacamma indicum is a tropical Ponerine ant species that lives in simple, single‐chambered nests with a single entrance. In this study, we characterised the mound architecture and performed field experiments to check functional significance of mounds.3. On examining mound architecture (n = 19 nests), we found that mounds not only elevated the nest entrance by 3.39 cm on average, but they also made the entrance at the top of the mound significantly smaller than the nest entrance at the base of the mound. Both these features are likely to reduce rainwater from falling directly into the nest's entrance tunnel.4. Upon performing partial (n = 18 nests) and complete destruction (n = 20 nests) in two different seasons, colonies were observed to actively rebuilt mounds to pre‐destruction levels within 3 days in all cases.5. Furthermore, examining the amount of water that entered the nest upon flooding in the presence and absence of mounds (n = 18 colonies) revealed that mounds prevented a minimum of 29.2% of water from seeping into the nest from the surrounding area, as mounds could act as a levee. This study highlights the active architectural adaptations to flooding by an organism that dwells in subterranean nests in a tropical habitat.