In memoriam Raphaël Boulay

Ant queen pheromones (QPs) have long been known to affect colony functioning. In many species, QPs affect important reproductive functions such as diploid larvae sexualization and egg-laying by workers, unmated queens (gynes), or other queens. Until the 1990s, these effects were generally viewed to be the result of queen manipulation through the use of coercive or dishonest signals. However, in their seminal 1993 paper, Keller and Nonacs challenged this idea, suggesting that QPs had evolved as honest signals that informed workers and other colony members of the queen's presence and reproductive state. This paper has greatly influenced the study of ant QPs and inspired numerous attempts to identify fertility-related compounds and test their physiological and behavioral effects. In the present article, the literature on ant QPs was reviewed in various contexts paying special attention to the role of cuticular hydrocarbons (CHCs). Although the controversy generated by Keller and Nonacs' paper is currently less intensively debated, there is still no clear evidence which allows the rejection of the queen control hypothesis in favor of the queen signal hypothesis. Important questions remain regarding the mode of action of QPs, and their targets which may help understanding their evolution. informacion[at]ebd.csic.es: Villalta et al (2018) Queen Control or Queen Signal in Ants: What Remains of the Controversy 25 Years After Keller and Nonacs' Seminal Paper? J Chem Ecol Doi 10.1007/s10886-018-0974-9