Predatory beetles can detect the unique alarm signal released by ants that are under attack by parasitic flies, and the beetles use those overheard conversations to guide their search for safe egg-laying sites on coffee bushes.Azteca instabilis ants patrol coffee bushes and emit chemical alarm signals when they're under attack by phorid flies. In an article published online July 27 in the journal Ecology and Evolution, University of Michigan researchers and their colleagues show that pregnant lady beetles intercept the ants' alarm pheromones, which let the beetles know that it's safe to deposit their eggs. The findings, which may have practical implications for pest management on coffee plantations, are the first documentation of a complex cascade of interactions mediated by ant pheromones, according to the authors.
An Azteca ant grabs an adult lady beetle on a coffee plant in Chiapas, Mexico. Lady beetles attempt to eat the green coffee scale insects guarded by the ants. But patrolling ants will attack and kill adult beetles and will remove beetle eggs laid on ant-tended coffee plants. the dynamics are discussed in Ecology and Evolution journal article, co-authored by SNRE Professor Ivette Perfecto.