Kovac, D., Klein, R.W., Rosli, H. & Wiwatwitaya, D.

Bamboo sap ejection from the nests of Tetraponera binghami (Hymenoptera: Formicidae: Pseudomyrmecinae) and the role of flood control in arboreal ants

Some tree-dwelling ants that live in plant cavities are known to use flood defences to prevent flooding of their nests by rain or seawater. Here, we report for the first time on a flood-defence technique used by the South-East Asian ant Tetraponera binghami to prevent flooding of its nest by bamboo sap. Tetraponera binghami workers bite entry holes into the walls of bamboo culm shoots of Dendrocalamus, Gigantochloa, and Cephalostachyum in order to nest in their cavities. As sap oozes from the damaged vascular bundles into the newly created entry holes, the internode cavities are at risk of flooding. To prevent this, T. binghami workers remain in the tubular entrance holes and expel the intruding sap from the nest with rapid pumping movements of their gaster. Meanwhile, they are immersed in the bamboo sap, and their bodies are partially enveloped in a layer of air held in place by hydrofuge hairs. We discuss how the unique sap ejection behaviour of T. binghami works and review other flood control methods used by arboreal ants. We propose that sophisticated flood control methods have evolved only in arboreal ants that nest in cavities in living plants that can hold water and have a nest entrance hole of the right size. Other factors, such as the amount of water run-off, the characteristics of the nest substrate, and the evolutionary history of the ants also influence the occurrence of flood control behaviour.

Open access, licensed under CC BY 4.0. © 2023 The Author(s).

Bamboo-internode nest, nest flooding, flood defence, abdominal pumping, hydrofuge hairs.