In the polymorphic harvester ant Messor barbarus, the colony modulates response during foraging according to seed characteristics. The easiness of picking up small seeds (oat fragments or canary seeds) shortens the time lapse between food discovery and the return of scouts to the nest, favouring the onset of recruitment and higher mobilisation rates than bigger seeds (whole oat). However, size ...

Recruitment to food or nest sites is well known in ants; the recruiting ants lay a chemical trail that other ants follow to the target site, or they walk with other ants to the target site. Here we report that a different process determines foraging direction in the harvester ant Pogonomyrmex barbatus. Each day, the colony chooses from among up to eight distinct foraging trails; colonies use di...

The variation in animal mating systems has received a great deal of attention from behaviorists and evolutionary biologists alike (Shuster & Wade 2003). Polyandry, the mating of a single female with multiple males, is evolutionarily derived (Hughes et al. 2008) and relatively rare in social insects (Strassmann 2001). Modest polyandry has evolved in Vespula wasps (Ross 1986; Foster & Ratnieks 20...

Structures influence how individuals interact and, therefore, shape the collective behaviours that emerge from these interactions. Here I show that the structure of a nest influences the collective behaviour of harvester ant colonies. Using network analysis, I quantify nest architecture and find that as chamber connectivity and redundancy of connections among chambers increase, so does a colony...

We examined the scale of recruitment limitation in the western harvester ant, Pogonomyrmex occidentalis (Cresson). We measured colony density of 98 plots (0.25 ha) over an area of 500 ha. By applying an interpolation/extrapolation analysis to the spatial variability in colony density, we were able to accurately identify the location of two mating swarms. These two swarms were 1,400 m apart. Con...

We investigated how foragers are activated in colonies of the red harvester ant, Pogonomyrmex barbatus. Each day, a harvester ant forager makes many trips out of the nest to gather seeds and bring them back to the nest. The rate at which foragers return to the nest is linked to food availability: when food is easy to find, foragers return more quickly. We examined how the return of successful a...