No specialist pheromone‐ignoring ants in Lasius niger

Abstract

In insect societies, the balance between exploitation of known resources and exploration of new ones is important to ensure sufficient resources. Mass recruiting ants, such as Lasius niger, use pheromone trails to recruit nestmates to a newly discovered food source. Pheromone following, however, shows characteristic non‐following (lapse) rates among different species, with ∼20% of L. niger foragers ignoring pheromone. These characteristic lapse rates might simply be ‘noise’, or they might indicate a subset of specialised explorative foragers, a scouting caste, that consistently ignores pheromone in order to explore. Here we show pheromone ignoring is not a repeatable behaviour in L. niger foragers – ants who did not follow a trail were no more likely to ignore it again an hour later than ants which did follow it. Our findings suggest that there is no subset of specialised pheromone‐ignoring L. niger foragers. This may be due to their moderate colony size and strong reliance on individual memories: species with larger colony sizes or a weaker reliance on private information (i.e. memory) may have specialist non‐followers. Our work raises the question: what is a scout ant? We encourage future research to investigate the presence of a scouting caste in other ant species using our straightforward methodology, as a social information‐ignoring caste may be rarer than expected.