Messor barbarus is a species of harvester ant in the subfamily Myrmicinae. It is found In Southern Europe and Northern Africa.
Messor barbarus causes 50–100% of the seed losses and is the most common ant in arable fields in northeastern Spain (Westerman et al. 2012). These ants in particular made news headlines all over Spain when farmers believed they were stealing their seeds and began a cull only to realise they actually play a massive part of the ecosystem and benefit the production for crop farmers completely. Messors will carry the seeds on their own roads back to the colony, sometimes up to 100ft away.
Messor barbarus is found to act in accordance with the optimal foraging theory, which predicts that selectivity in ants increases with increasing richness of resources in an area, as well as with increasing distance from starting location. Trails were likewise differentially favored according to the relative abundance of resources provided to the ant populations. Highly frequented trails had a higher mean rate per worker, meaning the harvesters returned higher rates of resources more efficiently along these trails. These trails drew more foraging ants to retrieve seeds on the whole, and the foraging ants returned seeds at a higher rate per capita. This foraging pattern indicates that relative food abundance along varying trails impacted the patterns of trail foraging behavior in Messor barbarus. For trails spanning long distances, ants exhibit behavior of strong chemical marking on preferred seeds to allow for the creation and maintenance of the route.
