Harvester Ant

Messor andrei

Hymenoptera: Formicidae

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Fighting Ants? Ron Hemberger reports…

As a kid growing up in the Midwest during the fifties, I was told that large and small ants would fight to the death when they came upon each other. What’s more, I saw this behavior time and time again. However, today in Orange County, I’ve often witnessed large and small ants in scenarios that looked like indifference or even cooperation, as opposed to hostility. I photographed such behavior, and showed the results to Richard Vernier. Note that the large ants shown are Messors, while the all-too-common Argentine ants are the smaller.

Richard Vernier comments…

This IS a life or death contest, although without (or almost without) any direct, overt aggression. And the smaller (Linepithema humile) will most likely be the winner. These photos perfectly illustrate how Argentine ants drive away other ant species. Although some Messor workers try desperately to save at least some of their brood, most of it will finish as food for the always hungry Argentine ants. What makes the seemingly much stronger harvesters so vulnerable are the chemical weapons of the pygmies, which belong to the "odorous" ants subfamily. Any species that did not co-evolve with Argentine ants is essentially defenseless against these chemicals. They act at once as poison and, in a more subtle way, as so-called "propaganda" substances, which disorganize and demotivate the defenders. Hence this lack of resistance, which looks indeed surprising from our own point of view.