Samplings: October 2007

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Wood ant clutches conifer resin, a natural disinfectant.

Arnaud Maeder

Wood ants are industrious food gatherers, but why do they bother lugging home inedible gobs of solid conifer resin? The answer, according to a new study, is that the resin disinfects the nest and helps keep the ants free from disease. Michel Chapuisat and Philippe Christe of the University of Lausanne in Switzerland and two colleagues collected adults and larvae of the wood ant Formica paralugubris in the Swiss Jura Mountains. The team placed the ants in experimental containers and exposed them to a bacterium and a fungus that killed most of them within a few weeks. But small pieces of resin added to half the containers greatly improved survival rates for larvae exposed to both the fungus and the bacterium, and for adults exposed to the bacterium. The resin seems to have antibiotic properties. The investigators think it might release volatile compounds that inhibit the growth of microorganisms in the nest. It’s also possible that the ants coat themselves with antibiotics when they touch resin gobs. A few other animals, such as starlings, line their nests with fresh leaves thought to hinder blood-sucking mites and fleas. Chapuisat and Christe’s ant study, however, is the first to prove that enlisting plant material to combat pathogens improves survival in a nonhuman animal. (Proceedings of the Royal Society B)