Adobe wall biodeterioration by the Centris muralis Burmeister bee (Insecta: Hymenoptera: Apidae) in a valuable colonial site, the Capayán ruins (La Rioja, Argentina)

Abstract

Historic earthen buildings in central western Argentina constitute a valuable resource for studies of recent material culture. Without adequate care and maintenance, these types of buildings are susceptible to damage by physical or biological processes. A specific type of damage was identified in earthen walls of the Capayán ruins, in La Rioja, Argentina. The aim of the present study was to determine the cause of this damage and understand the biodeterioration process. The wall selected for this study exhibited massive erosion in zones used by bees for nesting. These zones presented easily distinguishable patches of coarse appearance on the wall surface. A high density of cavities as a result of the removal of the cells (708 cavities m2, SD < 5%) was observed. The causal agent was identified as the bee Centris muralis Burmeister. The weight of the material lost from the wall due to biodeteriorationwas estimated at 729 kg of earth. Erosion in the attacked parts reduced the thickness of the adobe wall ca. 7 cm compared to parts without nests. This study demonstrates that earthen walls are subject not only to damage by weathering, but also to biodeterioration.