Author: Baudier, K.M. & Pavlic T.P. Year: 2020 DOI: 10.25849/myrmecol.news_030:251 Title: Incidental interactions among Neotropical army-ant colonies are met with self-organized walls of ants (Hymenoptera: Formicidae) Journal: Myrmecological News Volume: 30 Pages: 251-258 URL: www.myrmecologicalnews.org Keywords: Eciton, emergent structures, Labidus, Nomamyrmex, self-assembly, walling. Abstract: Warfare between social groups has long been a popular topic of study among ethologists, but less well studied are the mechanisms by which interacting groups maintain peace. We report on the use of transient living walls as a mechanism by which avoidance is established between army-ant mass raids and non-prey ant species commonly encountered in the environment (other army ants and leafcutter ants). These transient walls are composed of a series of individuals performing stereotyped posturing displays at the border between interacting colonies. Unlike preemptive column guarding by soldiers, these walls are composed of a variety of worker sub-castes and can arise and disappear rapidly in response to the presence of local threats. Quantified videos of in-field artificial introductions revealed that walking ants switch to the task of posturing within a wall following multiple contacts with non-nestmates and that posturing ants return to walking as contacts with intruders decline and contacts with nestmates increase. The rapid shift of army ants to the task of forming transient walls at the instant when they are needed for traffic management provides a highly observable system in which to study the rules of individual-based living constructions, providing potential insight into similar processes across levels of biological organization. Publisher: The Austrian Society of Entomofaunistics ISSN: 1997-3500