Can the Leaf-cutter Ant, Atta Cephalotes (Hymenoptera: Myrmicinae), Be Classified As An Urban Pest?

Abstract:
Agriculture in tropical regions has been associated with the rapid expansion of leaf-cutting ants in clearings since an initial report in 1587. Numerous studies document higher population densities in human-simplified habitats than in natural ones, usually producing economical losses in agricultural crops”. Apart from this, little else is known about other impacts of these ants in urban environments. However, when confronted with the World Health Organization definition of urban pests (i.e. those species implicated in the transfer of diseases, habitat damage or human welfare deterioration, with a continuous presence and population sizes above –the considered– normal levels) it becomes evident that some leaf-cutting species, at least Atta cephalotes meet WHO’s criteria and should be considered as an urban pest. In order to elude the circular argument, “the lack of data preclude any meaningful discussion”, we reviewed and analyzed literature recording the presence of leaf-cutting ants in Colombian urban areas but especially in Cali. Information related to A. cephalotes was processed and analyzed apart. We found that A. cephalotes, a lowland species, is now widespread in rural and urban areas of many Colombian cities below 1600 m.a.s.l. Presumably, this is a response to both urban development and climate change. The ants were observed taking advantage of human environments modified through gardening practices, urban constructions and the disappearance of their natural enemies. A. cephalotes is abundant and affects urban and home gardens. In some instances, they have been observed invading houses, hospitals and other buildings. Ants display a high polyphagy, enhanced by their intrinsic capacity to attack both native and exotic plant species and their immense ability to flourish on manufactured products (e.g. oat flakes) whenever these are available. In addition, under urban conditions colonies exhibit rapid and successful dynamic cycles, demanding more resources and have the physiological and behavioural capacity to withstand control methods and take advantage of the population decline of their natural enemies. Ant colonies aggregated in river flanks have weakened the civil engineering structures constructed to hold the river bed, representing a serious threat to nearby dwellers. These facts predispose us to consider A. cephalotes, arguably, as the most problematic urban pest in Cali, Colombia.